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Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

CHEMISTRY 9701/11

Paper 1 Multiple Choice October/November 2015

1 hour

Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended) Data Booklet

READ THESE INSTRUCTIONS FIRST

Write in soft pencil.

Do not use staples, paper clips, glue or correction fluid.

Write your name, Centre number and candidate number on the Answer Sheet in the spaces provided unless this has been done for you.

DO NOT WRITE IN ANY BARCODES.

There are forty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D.

Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet.

Read the instructions on the Answer Sheet very carefully.

Each correct answer will score one mark. A mark will not be deducted for a wrong answer.

Any rough working should be done in this booklet.

Electronic calculators may be used.

2

© UCLES 2015 9701/11/O/N/15

Section A For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 The table gives the successive ionisation energies for an element X.

1st 2nd 3rd 4th 5th 6th

ionisation energy / kJ mol–1 950 1800 2700 4800 6000 12 300

What could be the formula of a chloride of X?

A XCl B XCl 2 C XCl 3 D XCl 4 2 Which set of conditions gives the highest yield of ammonia at equilibrium?

N2(g) + 3H2(g) 2NH3(g) ∆H

o = –92 kJ mol–1

catalyst pressure temperature

A absent high low

B absent low high

C present high high

D present low low

3 Use of the Data Booklet is relevant to this question.

The compound S2O7 is hydrolysed by water to produce sulfuric acid and oxygen only.

Which volume of oxygen, measured at room temperature and pressure, is evolved when 0.352 g of S2O7 is hydrolysed?

A 12 cm3 B 24 cm3 C 48 cm3 D 96 cm3 4 Nitrogen, N2, and carbon monoxide, CO, both have Mr = 28.

The boiling point of N2 is 77 K.

The boiling point of CO is 82 K.

What could be responsible for this difference in boiling points?

A CO molecules have a permanent dipole, the N2 molecules are not polar.

B N2 has σ and π bonding, CO has σ bonding only.

C N2 has a strong N≡N bond, CO has a C=O bond.

D The CO molecule has more electrons than the N2 molecule.

3

© UCLES 2015 9701/11/O/N/15 [Turn over

5 Some car paints contain small flakes of silica, SiO2.

In the structure of solid SiO2

● each silicon atom is bonded to x oxygen atoms,

● each oxygen atom is bonded to y silicon atoms,

● each bond is a z type bond.

What is the correct combination of x, y and z in these statements?

x y z

A 2 1 covalent

B 2 1 ionic

C 4 2 covalent

D 4 2 ionic

6 Solid sulfur consists of molecules made up of eight atoms covalently bonded together.

The bonding in sulfur dioxide is O=S=O.

enthalpy change of combustion of S8, S8(s)= –2376kJ mol–1

energy required to break 1 mole S8(s) into gaseous atoms = 2232 kJ mol–1

O=O bond enthalpy = 496 kJ mol–1

Using these data, what is the value of the S=O bond enthalpy?

A 239 kJ mol–1 B 257 kJ mol–1 C 319 kJ mol–1 D 536 kJ mol–1 7 Use of the Data Booklet is relevant for this question.

In an experiment, the burning of 1.45 g (0.025 mol) of propanone was used to heat 100 g of water.

The initial temperature of the water was 20.0 °C and the final temperature of the water was

78.0 °C.

Which experimental value for the enthalpy change of combustion for propanone can be calculated from these results?

A –1304 kJ mol–1

B –970 kJ mol–1

C –352 kJ mol–1

D –24.2 kJ mol–1

4

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8 Which row correctly describes the electrodes that can be used in a diaphragm cell for the production of chlorine, hydrogen and sodium hydroxide?

anode cathode

A steel graphite

B steel titanium

C titanium graphite

D titanium steel

9 Hexamine is a crystalline solid used as a fuel in portable stoves.

The diagram shows its skeletal structure.

N

NN N

What is the empirical formula of hexamine?

A CH2N B C3H6N2 C C4H8N4 D C6H12N4 10 A mixture of nitrogen and hydrogen gases, at a temperature of 500 K, was put into an evacuated

vessel of volume 6.0 dm3. The vessel was then sealed.

N2(g) + 3H2(g) 2NH3(g)

The mixture was allowed to reach equilibrium. It was found that 7.2 mol of N2 and 12.0 mol of H2 were present in the equilibrium mixture. The value of the equilibrium constant, Kc, for this

equilibrium is 6.0 × 10–2 at 500 K.

What is the concentration of ammonia present in the equilibrium mixture at 500 K?

A 0.58 mol dm–3

B 0.76 mol dm–3

C 3.5 mol dm–3

D 27 mol dm–3

5


11 Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.

N2(g) + 3H2(g) 2NH3(g) ∆H –ve

What will increase the rate of the forward reaction?

A adding argon to the mixture but keeping the total volume constant

B decreasing the temperature

C increasing the total pressure by reducing the total volume at constant temperature

D removing ammonia as it is made but keeping the total volume of the mixture the same 12 X is a Group II metal. The carbonate of X decomposes when heated in a Bunsen flame to give

carbon dioxide and a white solid residue as the only products. This white solid residue is sparingly soluble in water. Even when large amounts of the solid residue are added to water the pH of the saturated solution is less than that of limewater.

What could be the identity of X?

A magnesium

B calcium

C strontium

D barium 13 Rat poison needs to be insoluble in rain water but soluble at the low pH of stomach contents.

What is a suitable barium compound to use for rat poison?

A barium carbonate

B barium chloride

C barium hydroxide

D barium sulfate 14 Use of the Data Booklet is relevant to this question.

Which of the elements sodium, magnesium, aluminium, silicon, phosphorus, sulfur and chlorine

• has a lower first ionisation energy than the preceding element in the Periodic Table,

• conducts electricity and

• has a lower atomic radius than the preceding element in the Periodic Table?

A aluminium

B magnesium

C phosphorus

D sulfur

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15 The melting points of the Period 3 elements sodium to aluminium are shown in the table.

element Na Mg Al

mp / K 371 923 932

Which factor explains the increase in melting points from sodium to aluminium?

A the changes in first ionisation energy from sodium to aluminium

B the increase in electronegativity from sodium to aluminium

C the increase in the Ar of the elements from sodium to aluminium

D the increase in the number of outer electrons in each atom from sodium to aluminium 16 X is the oxide of a Period 3 element. X reacts with water to give an acidic solution.

A solution is prepared by reacting 0.100 g of X with excess water. This solution was neutralised by exactly 25.0 cm3 of 0.100 mol dm–3 sodium hydroxide solution.


A Al 2O3 B MgO C P4O10 D SO3 17 Which statement about bromine is correct?

A Bromine is insoluble in non-polar solvents.

B Bromine vapour is more dense than air.

C Bromine will not vaporise significantly under normal conditions.

D Gaseous bromine is purple. 18 The addition of aqueous silver nitrate to aqueous barium chloride produces a white precipitate

which dissolves in excess dilute aqueous ammonia to form a colourless solution.

The addition of excess dilute nitric acid to the colourless solution produces a white precipitate, Z.

What is Z?

A AgCl B BaCl 2 C Ba(NO3)2 D NH4NO3

7


19 Element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statements.

Student P ‘The molecule of Y contains lone pairs of electrons.’

Student Q ‘The oxidation number of X increases by 1 from Y to Z.’

X could be carbon or nitrogen or sulfur.

Which student(s) made a correct statement?

A P only

B Q only

C both P and Q

D neither P nor Q 20 How many isomeric esters have the molecular formula C4H8O2?

A 2 B 3 C 4 D 5 21 A new jet fuel has been produced that is a mixture of different structural isomers of compound Q.

Q

Which skeletal formula represents a structural isomer of Q?

A B

C D

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22 Crude oil is a mixture of many hydrocarbons ranging in size from 1 to 40 carbon atoms per molecule. The alkanes in crude oil can be separated because they have different boiling points.

The table below shows the boiling points of some alkanes.

alkane boiling point

/ °C Mr

butane 0 58

pentane 36 72

hexane 69 86

2-methylbutane 28 72

dimethylpropane 10 72

2,3-dimethylbutane 58 86

What is the correct explanation for the difference in the boiling points of the three isomers with Mr = 72?

A Boiling point is dependent upon the length of the carbon chain only.

B Increased branching on a carbon chain increases the boiling point.

C Increased branching reduces the strength of the intermolecular hydrogen bonding.

D Increased branching reduces the strength of the intermolecular van der Waals’ forces. 23 Compound Q contains three double bonds per molecule.

CH2 CH2CH CH2C

O O

C OHX Y

Q

Which bond, X or Y, will be ruptured by hot, concentrated acidified KMnO4 and how many lone pairs of electrons are present in one molecule of Q?

bond ruptured by hot,

concentrated acidified KMnO4 number of lone pairs

A X 5

B X 6

C Y 5

D Y 6

9


24 Which compound undergoes an SN1 substitution reaction with NaOH(aq)?

A CH3CH2CH2Br

CH2=CHCl

B (CH3)3CCH2I

C

CH3 Cl

D

25 If the starting material is iodoethane, which sequence of reactions will produce propanoic acid as

the main final product in good yield?

A add NaOH(aq), isolate the organic product, add acidified K2Cr2O7 and boil under reflux

B add NaOH(aq), isolate the organic product, add H2SO4(aq) and boil under reflux

C heat with HCN in ethanol, isolate the organic product, add H2SO4(aq) and boil under reflux

D heat with KCN in ethanol, isolate the organic product, add H2SO4(aq) and boil under reflux

26 Which compound cannot be oxidised by acidified potassium dichromate(VI) solution but does

react with sodium metal?

A (CH3)3COH

B CH3COCH2CH3

C CH3CH2CH2CH2OH

D CH3CH2CH(OH)CH3 27 Butan-2-ol can be made by reducing X with H2 / Ni.

Butan-2-ol can be dehydrated to form Y and Z which are structural isomers of each other.

Which row is correct?

X is cis-trans isomerism

is shown by

A an aldehyde both Y and Z

B an aldehyde only one of Y and Z

C a ketone both Y and Z

D a ketone only one of Y and Z

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28 Tollens’ reagent can be used to help identify compounds P, Q and R.

C

O

P

HH3CC

O

Q

CH3

CH3

H3C

H3C

R

C

H

OH

Which compound(s) form a silver precipitate on warming with Tollens’ reagent?

A P and Q B P only C Q only D R only 29 Sorbitol is a naturally-occurring compound with a sweet taste. It is often used as a substitute for

sucrose by the food industry.

H C

H

OH

OH

OH

OH

OH

OH

H C

H C

H C

H C

H C

H

sorbitol

How many chiral centres are present in sorbitol?

A 3 B 4 C 5 D 6 30 Which compound produces butan-2-ol and ethanoic acid on hydrolysis?

A CH3CO2CH(CH3)2

B CH3CO2CH(CH3)CH2CH3

C CH3CH(CH3)CO2CH2CH3

D CH3CH2CO2CH(CH3)CH2CH3

11


Section B For each of the questions in this section, one or more of the three numbered statements 1 to 3 may be correct. Decide whether each of the statements is or is not correct (you may find it helpful to put a tick against the statements that you consider to be correct). The responses A to D should be selected on the basis of

A B C D

1, 2 and 3 are

correct

1 and 2 only are correct


1 only is

correct

No other combination of statements is used as a correct response. 31 Which statements about orbitals in a krypton atom are correct?

1 The 1s and 2s orbitals have the same energy as each other but different sizes.

2 The third energy level (n=3) has three subshells and nine orbitals.

3 The 3d subshell has five orbitals that have the same energy as each other in an isolated atom.

32 The Group IV elements carbon, silicon and germanium can all exist in the giant molecular

structure which is also found in diamond. The bond lengths in these structures are given below.

element X C Si Ge

bond length X–X / nm 0.154 0.234 0.244

Why does the bond length increase down the group?

1 Orbital overlap decreases down the group.

2 Atomic radius increases down the group.

3 Nuclear charge increases down the group.

12

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The responses A to D should be selected on the basis of

A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 33 The salt NaCl O3 is used as a non-selective weedkiller.

On careful heating, this reaction occurs: 4NaCl O3 → NaCl + 3NaCl O4.

On strong heating this reaction occurs: NaCl O4 → NaCl + 2O2.

The overall reaction is 2NaCl O3 → 2NaCl + 3O2.

What do these equations show?

1 NaCl O3 can behave as an oxidising agent.

2 NaCl O3 can behave as a reducing agent.

3 The oxidation numbers of chlorine in the three compounds shown are +6, +8 and –1. 34 Which statements correctly describe an effect of a rise in temperature on a gas-phase reaction?

1 More particles now have energies greater than the activation energy.

2 The energy distribution profile changes with more particles having the most probable energy.

3 The activation energy of the reaction is decreased. 35 Which statements concerning the Group II elements magnesium, calcium and barium are

correct?

1 Their reactivity increases with increasing relative atomic mass.

2 The oxidation number exhibited in their stable compounds is +2.

3 On strong heating, their nitrates give off oxygen only. 36 Sulfur dioxide is used as a food preservative.

Which statements about sulfur dioxide, SO2, are correct?

1 SO2 behaves as an antioxidant.

2 Aqueous SO2 contains SO32– ions.

3 SO2 inhibits the growth of mould and yeasts.

13

© UCLES 2015 9701/11/O/N/15

37 An oxidising agent that can oxidise ethanal to ethanoic acid, or to ethanoate ions, will also oxidise methanoic acid, HCO2H, to carbon dioxide and water.

Which reagents, on heating, will react differently with HCO2H and CH3CO2H?

1 Na2CO3(aq)

2 Fehling’s reagent

3 dilute acidified KMnO4 38 Each of the compounds below is treated separately with excess NaBH4. The product of each

reaction is then heated with excess concentrated H2SO4.

In each case, one or more products are formed with molecular formula C7H10.

Which compounds give only one final product with the molecular formula C7H10?

1

O

O

2

O

O

3

O

O 39 Which reactions result in the formation of propanoic acid?

1 CH3CH2CO2Na with dilute H2SO4(aq)

2 CH3CH=CHCH3 with hot, concentrated H+ / MnO4

–(aq)

3 CH3CH2OH with H+ / Cr2O7

2–(aq) 40 The diagram shows the structure of propanamide.

H

H

H

C

H

H

H O

H

C C N

propanamide

Which statements about the hydrolysis of propanamide are correct?

1 Propanamide can be hydrolysed by heating under reflux with H2SO4(aq).

2 Propanamide can be hydrolysed by heating under reflux with NaOH(aq).

3 Propanamide can be hydrolysed by cold water.

14

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Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

© UCLES 2015 9701/11/O/N/15

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IB15 11_9701_12_A3/FP

© UCLES 2015 [Turn over

*6952395883*

Cambridge International Examinations

Cambridge International Advanced Subsidiary and Advanced Level

CHEMISTRY 9701/12


1 hour

Additional Materials: Multiple Choice Answer Sheet

Soft clean eraser

Soft pencil (type B or HB is recommended)

Data Booklet




Write your name, Centre number and candidate number on the Answer Sheet in the spaces provided

unless this has been done for you.


There are forty questions on this paper. Answer all questions. For each question there are four possible

answers A, B, C and D.






2

© UCLES 2015 9701/12/O/N/15

Section A

For each question there are four possible answers, A, B, C, and D. Choose the one you consider to

be correct.

1 Which type of bonding is never found in elements?

A covalent

B ionic

C metallic

D van der Waals’ forces

2 Arsenic chloride, AsCl 3, reacts with sodium borohydride, NaBH4.

pAsCl 3 + qNaBH4 → rAsH3 + sNaCl + tBCl 3

What are the numbers p, q, r, s and t when this equation is balanced correctly?

p q r s t

A 2 3 2 3 1

B 3 3 3 3 2

C 4 3 4 3 3

D 4 4 4 4 3

3 Three substances have the physical properties shown in the table.

substance

melting point

/ °C

boiling point

/ °C

conductivity

(solid)

conductivity

(liquid)

conductivity

(aqueous)

U 420 907 good good insoluble

V 993 1695 poor good good

W –70 58 poor poor hydrolyses, resulting

solution conducts well

What could be the identities of U, V and W?

U V W

A Na KCl SiCl 4

B Na NaF C2H5Br

C Zn KCl HCl

D Zn NaF SiCl 4

3


4 Flask X contains 5 dm3

of helium at 12 kPa pressure and flask Y contains 10 dm3

of neon at 6 kPa

pressure.

If the flasks are connected at constant temperature, what is the final pressure?

A 8 kPa B 9 kPa C 10 kPa D 11 kPa

5 Calcium forms an ionic compound with carbon, called calcium carbide. The oxidation number of

carbon in calcium carbide is –1.

Calcium carbide is readily hydrolysed by water giving two products only.

What could be the formulae of calcium carbide and the two products of hydrolysis?

calcium carbide products

A Ca2C CaO and C2H4

B Ca2C Ca(OH)2 and C2H2

C CaC2 CaO and C2H4

D CaC2 Ca(OH)2 and C2H2

6 Hess’ law may be used to determine enthalpy changes using average bond energies, as shown

in the diagram.

isolated gaseous atoms

reactants products

U V

W

U is the sum of the average bond energies of the reactants, and V is the sum of the average

bond energies of the products.

For the reaction shown below, which expression will give a value for W, the enthalpy change of

combustion of methane?

CH4 + 2O2 → CO2 + 2H2O

A U – V B U + V C 2(U – V) D V – U

4

© UCLES 2015 9701/12/O/N/15

7 The process of electrolysis can be used to purify copper, and to extract aluminium from an

aluminium oxide / cryolite mixture.

What are the reactions at the anode in each of these processes?

purification of copper extraction of aluminium

A Cu2+

+ 2e–

→ Cu 2O2–

→ O2 + 4e–

B Cu2+

+ 2e–

→ Cu 4OH–

→ O2 + 2H2O + 4e–

C Cu → Cu2+

+ 2e–

2O2–

→ O2 + 4e–

D Cu → Cu2+

+ 2e–

4OH–

→ O2 + 2H2O + 4e–

8 Hydrogen can be obtained by reacting methane with steam.

CH4(g) + H2O(g) CO(g) + 3H2(g) ΔH

o

= +210 kJ mol–1

Which conditions of pressure and temperature will give the greatest equilibrium yield of hydrogen?

pressure temperature

A high high

B high low

C low high

D low low

9 Nitrogen monoxide reacts with oxygen in a reversible reaction according to the equation shown

below.

2NO(g) + O2(g) 2NO2(g)

The partial pressures of each of the components in an equilibrium mixture are shown in the table.

partial pressure NO / kPa partial pressure O2

/ kPa partial pressure NO2

/ kPa

10 30 20

What is the numerical value of the equilibrium constant, Kp, for this equilibrium?

A 6.67 × 10–2

B 1.33 × 10–1

C 7.50 D 15.0

5


10 The decomposition reaction SF6(g) → SF4(g) + F2(g) can be described by the reaction

pathway diagram shown.

extent of reaction

energySF4(g) + F2(g)

SF6(g)

X

Y

What are the values of ΔH

o

and Ea for this reaction?

ΔH

o

Ea

A X X + Y

B X Y

C X – Y X

D Y – X X

11 Which row correctly describes what happens when the temperature of a chemical reaction is

decreased?

activation energy

(Ea)

number of

successful collisions

A decreases decreases

B decreases increases

C remains the same decreases

D remains the same increases

12 Which property decreases on descending Group II?

A radius of the cation, M2+

B reactivity of the element with water

C shielding of outermost electrons

D the ease of thermal decomposition of the carbonates, MCO3

6

© UCLES 2015 9701/12/O/N/15


The reaction between aluminium powder and anhydrous barium nitrate is used as the propellant

in some fireworks. The metal oxides and nitrogen are the only products.

Which volume of nitrogen, measured under room conditions, is produced when 0.783 g of

anhydrous barium nitrate reacts with an excess of aluminium?

A 46.8 cm3

B 72.0 cm3

C 93.6 cm3

D 144 cm3

14 Which chloride of a Period 3 element dissolves in water to form a solution with a pH of 7?

A aluminium chloride

B phosphorus(V) chloride

C silicon(IV) chloride

D sodium chloride


Which row correctly compares the electrical conductivity and first ionisation energy of magnesium

and aluminium?

higher electrical

conductivity

higher first

ionisation energy

A aluminium aluminium

B aluminium magnesium

C magnesium aluminium

D magnesium magnesium

7



Brine is concentrated aqueous sodium chloride.

In the commercial electrolysis of brine, the products are chlorine, hydrogen and sodium

hydroxide.

What is the maximum yield of each of these products when 58.5 kg of sodium chloride are

electrolysed as brine?

yield of

chlorine / kg

yield of

hydrogen / kg

yield of sodium

hydroxide / kg

A 35.5 1 40

B 35.5 2 40

C 71 1 40

D 71 2 80

17 A student observed the reactions when sodium chloride and sodium iodide were each reacted

separately with concentrated sulfuric acid and with concentrated phosphoric acid. Some

observations are recorded in the table.

sodium chloride sodium iodide

conc. H2SO4 colourless acidic gas formed purple vapour formed

conc. H3PO4 colourless acidic gas formed colourless acidic gas formed

Which deduction can be made from these observations?

A Concentrated phosphoric acid is a stronger oxidising agent than concentrated sulfuric acid.

B Concentrated phosphoric acid is a stronger oxidising agent than iodine.

C Concentrated sulfuric acid is a stronger oxidising agent than chlorine.

D Concentrated sulfuric acid is a stronger oxidising agent than iodine.

18 A white powder is a mixture of sodium chloride and sodium iodide. It is dissolved in water in a

test-tube. Excess aqueous silver nitrate is added to the test-tube. A precipitate, X, is observed.

Excess concentrated ammonia is then added to the test-tube containing X. After the test-tube has

been shaken, a precipitate, Y, is observed.

Which statement about X or Y is correct?

A X is a pure white colour.

B X is pure silver iodide.

C Y is pure silver chloride.

D Y is yellow.

8

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4.70 g of an ammonium salt is heated with excess aqueous sodium hydroxide. The volume of

ammonia gas given off, measured at room temperature and pressure, is 1.41 dm3

.

Which ammonium salt was used?

A ammonium bromide (Mr = 97.9)

B ammonium carbonate (Mr = 96)

C ammonium nitrate (Mr = 80)

D ammonium sulfate (Mr = 132.1)

20 Which ester is formed when the alcohol CH3CH2OH is reacted with CH3CH2CH2CO2H?

A butyl ethanoate

B ethyl butanoate

C ethyl propanoate

D propyl ethanoate

21 Which compound shows optical isomerism?

A 2-chloropropane

B 1,2-dichloropropane

C 1,3-dichloropropane

D 2,2-dichloropropane

22 Methanoic acid, HCO2H, has acidic properties similar to those of other carboxylic acids. In

addition it can be oxidised by the same oxidising agents that are capable of oxidising aldehydes.

Which pair consists of two compounds that will give the same observations with Fehling’s

reagent?

A HCO2H and CH3CO2H

B HCO2H and CH3CO2CH3

C HCO2H and CH3CH2COCH3

D HCO2H and CH3CH2CHO

9


23 Compound Q can be made from propanone.

O

Q

Which types of reaction will Q undergo?

A nucleophilic addition and electrophilic addition

B nucleophilic addition and nucleophilic substitution

C nucleophilic addition only

D nucleophilic substitution and electrophilic addition

24 The depletion of the ozone layer in the upper atmosphere reduces the Earth’s natural protection

from harmful ultraviolet radiation.

Which compound would cause the most depletion of the ozone layer?

A CCl 3F B CF4 C CO2 D SO2

10

© UCLES 2015 9701/12/O/N/15

25 Compound X has been investigated for use as an artificial sweetener.

OH

OH

OHO

OCl

Cl

OH

OH

O

X

The two C–Cl bonds can be hydrolysed by hot NaOH(aq). The C-O-C bonds cannot be

hydrolysed by hot NaOH(aq).

What are the numbers of specified types of –OH groups before and after hydrolysing the two

C–Cl bonds?

before

hydrolysis

after hydrolysis

secondary primary secondary tertiary

A 0 1 2 4

B 0 2 1 4

C 4 1 5 1

D 4 2 4 1

26 The compounds below are all produced by plants.

Each compound is warmed with acidified potassium dichromate(VI).

Which compound will give a different observation to the other three?

OH

A

OH

B C D

OH

OH

11


27 What is the mechanism for the reaction of ethanal, CH3CHO, with hydrogen cyanide, HCN, in the

presence of a base?

A CH3

CN–

C H

O

CH3

CN

C H

O–

CH3

CN

C H

–O

CH3

CN

C H

OH

CH3

CN

C H

OH

H–

C

CH3

CN–

C H

H CH3

CN–

C H

OHO

CH3 C +

O

CN

D initiation HCN H

H

+ CN

CNpropagation

termination

CH3C +

O

H

CH3C

O

CN

H

CH3C H +

CN–B +

H C N

CH3

H C

C

N

•

•

•

HCH3C CNH + CN+

CH3C

OH

CN

H

CH3C

OH

CN

H •

•

O

CN

•

O

CN

•

•

+

O

12

© UCLES 2015 9701/12/O/N/15

28 Menthol and menthone are both found in peppermint oil.

OH

menthol

O

menthone

Which statement about these compounds is correct?

A Both compounds can undergo mild oxidation.

B Both compounds will give an orange precipitate with 2,4-dinitrophenylhydrazine reagent.

C Menthol can be formed from menthone by reaction with NaBH4.

D Menthone gives a positive test when warmed with Tollens’ reagent.

29 What is the skeletal formula of 2-methylpentan-1-ol?

OH

A

OH

B

OH OH

C D

30 The structure of aspartame, which is used as an artificial sweetener, is shown.

O OCH3

NH2

C6H5

OH O

NH

O1 2

aspartame

If aspartame is warmed in aqueous alkali, which of bonds 1 and 2 will be broken?

A both bond 1 and bond 2

B bond 1 only

C bond 2 only

D neither bond 1 nor bond 2

13


Section B

For each of the questions in this section, one or more of the three numbered statements 1 to 3 may

be correct.

Decide whether each of the statements is or is not correct (you may find it helpful to put a tick against

the statements that you consider to be correct).


A B C D

1, 2 and 3

are

correct

1 and 2

only are

correct

2 and 3

only are

correct

1 only

is

correct

No other combination of statements is used as a correct response.

31 The relative molecular mass, Mr, of a particular sample of chlorine is 72.0.

Which properties of the atoms in this sample will be the same for all of the atoms?

1 radius

2 nucleon number

3 isotopic mass

32 Which of the following influence the size of the ionisation energy of an atom?

1 the amount of shielding by the inner electrons

2 the charge on the nucleus

3 the distance between the outer electrons and the nucleus

33 Which equations can apply to an ideal gas?

[p = pressure, V = volume, M = molar mass, ρ = density, c = concentration, R = gas constant,

T = temperature]

1 p =

M

RTρ

2 pV =

M

cRT 3 pV = MRT

14

© UCLES 2015 9701/12/O/N/15


A B C D

1, 2 and 3

are

correct

1 and 2

only are

correct

2 and 3

only are

correct

1 only

is

correct

No other combination of statements is used as a correct response.

34 Ammonia and chlorine react in the gas phase.

8NH3 + 3Cl 2 → N2 + 6NH4Cl

Which statements are correct?

1 Each nitrogen atom is oxidised.

2 Each chlorine atom is reduced.

3 Ammonia behaves as a base.

35 Which statements about calcium and strontium compounds are correct?

1 When calcium oxide and strontium oxide are added to water they both produce alkalis.

2 Calcium hydroxide is more soluble than strontium hydroxide.

3 Calcium sulfate is less soluble than strontium sulfate.

36 Which descriptions of the ammonium ion are correct?

1 It contains ten electrons.

2 It has a bond angle of 109.5°.

3 It has only three bonding pairs of electrons.

37 Compound Q is obtained by adding H2O across the double bond in compound P.

OH

P Q

Which statements about these two compounds are correct?

1 P shows cis-trans isomerism.

2 Q contains two chiral centres.

3 Q is a tertiary alcohol.

15

© UCLES 2015 9701/12/O/N/15

38 X is an organic compound. X gives a precipitate with aqueous silver nitrate. Some or all of this

precipitate remains undissolved when excess dilute aqueous ammonia is added.


1 2-chlorobutane

2 2-bromobutane

3 iodomethane

39 Which compounds, on heating with excess concentrated sulfuric acid, produce only one product

with molecular formula C7H10?

3

OH

OH

OH

OHOH

OH

1 2

40 Compound Z is heated with concentrated acidified potassium manganate(VII). This produces an

equimolar mixture of CO2 and CH3COCH2CH2CH(COCH3)CH2CO2H.

What could be the structural formula of Z?

1 2 3

16

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every

reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the

publisher will be pleased to make amends at the earliest possible opportunity.

To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge

International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at

www.cie.org.uk after the live examination series.

Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local

Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

© UCLES 2015 9701/12/O/N/15

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IB15 11_9701_13/5RP © UCLES 2015 [Turn over

*8050022522*

Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

CHEMISTRY 9701/13


1 hour

Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended) Data Booklet




Write your name, Centre number and candidate number on the Answer Sheet in the spaces provided unless this has been done for you.


There are forty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D.






2

© UCLES 2015 9701/13/O/N/15

Section A For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 The table gives the successive ionisation energies for an element X.

1st 2nd 3rd 4th 5th 6th

ionisation energy / kJ mol–1 950 1800 2700 4800 6000 12 300

What could be the formula of a chloride of X?

A XCl B XCl 2 C XCl 3 D XCl 4 2 Which set of conditions gives the highest yield of ammonia at equilibrium?

N2(g) + 3H2(g) 2NH3(g) ∆H

o = –92 kJ mol–1

catalyst pressure temperature

A absent high low

B absent low high

C present high high

D present low low


The compound S2O7 is hydrolysed by water to produce sulfuric acid and oxygen only.

Which volume of oxygen, measured at room temperature and pressure, is evolved when 0.352 g of S2O7 is hydrolysed?

A 12 cm3 B 24 cm3 C 48 cm3 D 96 cm3 4 Nitrogen, N2, and carbon monoxide, CO, both have Mr = 28.

The boiling point of N2 is 77 K.

The boiling point of CO is 82 K.

What could be responsible for this difference in boiling points?

A CO molecules have a permanent dipole, the N2 molecules are not polar.

B N2 has σ and π bonding, CO has σ bonding only.

C N2 has a strong N≡N bond, CO has a C=O bond.

D The CO molecule has more electrons than the N2 molecule.

3


5 Some car paints contain small flakes of silica, SiO2.

In the structure of solid SiO2

● each silicon atom is bonded to x oxygen atoms,

● each oxygen atom is bonded to y silicon atoms,

● each bond is a z type bond.

What is the correct combination of x, y and z in these statements?

x y z

A 2 1 covalent

B 2 1 ionic

C 4 2 covalent

D 4 2 ionic

6 Solid sulfur consists of molecules made up of eight atoms covalently bonded together.

The bonding in sulfur dioxide is O=S=O.

enthalpy change of combustion of S8, S8(s)= –2376kJ mol–1

energy required to break 1 mole S8(s) into gaseous atoms = 2232 kJ mol–1

O=O bond enthalpy = 496 kJ mol–1

Using these data, what is the value of the S=O bond enthalpy?

A 239 kJ mol–1 B 257 kJ mol–1 C 319 kJ mol–1 D 536 kJ mol–1 7 Use of the Data Booklet is relevant for this question.

In an experiment, the burning of 1.45 g (0.025 mol) of propanone was used to heat 100 g of water.

The initial temperature of the water was 20.0 °C and the final temperature of the water was

78.0 °C.

Which experimental value for the enthalpy change of combustion for propanone can be calculated from these results?

A –1304 kJ mol–1

B –970 kJ mol–1

C –352 kJ mol–1

D –24.2 kJ mol–1

4

© UCLES 2015 9701/13/O/N/15

8 Which row correctly describes the electrodes that can be used in a diaphragm cell for the production of chlorine, hydrogen and sodium hydroxide?

anode cathode

A steel graphite

B steel titanium

C titanium graphite

D titanium steel

9 Hexamine is a crystalline solid used as a fuel in portable stoves.

The diagram shows its skeletal structure.

N

NN N

What is the empirical formula of hexamine?

A CH2N B C3H6N2 C C4H8N4 D C6H12N4 10 A mixture of nitrogen and hydrogen gases, at a temperature of 500 K, was put into an evacuated

vessel of volume 6.0 dm3. The vessel was then sealed.

N2(g) + 3H2(g) 2NH3(g)

The mixture was allowed to reach equilibrium. It was found that 7.2 mol of N2 and 12.0 mol of H2 were present in the equilibrium mixture. The value of the equilibrium constant, Kc, for this

equilibrium is 6.0 × 10–2 at 500 K.

What is the concentration of ammonia present in the equilibrium mixture at 500 K?

A 0.58 mol dm–3

B 0.76 mol dm–3

C 3.5 mol dm–3

D 27 mol dm–3

5


11 Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.

N2(g) + 3H2(g) 2NH3(g) ∆H –ve

What will increase the rate of the forward reaction?

A adding argon to the mixture but keeping the total volume constant

B decreasing the temperature

C increasing the total pressure by reducing the total volume at constant temperature

D removing ammonia as it is made but keeping the total volume of the mixture the same 12 X is a Group II metal. The carbonate of X decomposes when heated in a Bunsen flame to give

carbon dioxide and a white solid residue as the only products. This white solid residue is sparingly soluble in water. Even when large amounts of the solid residue are added to water the pH of the saturated solution is less than that of limewater.


A magnesium

B calcium

C strontium

D barium 13 Rat poison needs to be insoluble in rain water but soluble at the low pH of stomach contents.

What is a suitable barium compound to use for rat poison?

A barium carbonate

B barium chloride

C barium hydroxide

D barium sulfate 14 Use of the Data Booklet is relevant to this question.

Which of the elements sodium, magnesium, aluminium, silicon, phosphorus, sulfur and chlorine

• has a lower first ionisation energy than the preceding element in the Periodic Table,

• conducts electricity and

• has a lower atomic radius than the preceding element in the Periodic Table?

A aluminium

B magnesium

C phosphorus

D sulfur

6

© UCLES 2015 9701/13/O/N/15

15 The melting points of the Period 3 elements sodium to aluminium are shown in the table.

element Na Mg Al

mp / K 371 923 932

Which factor explains the increase in melting points from sodium to aluminium?

A the changes in first ionisation energy from sodium to aluminium

B the increase in electronegativity from sodium to aluminium

C the increase in the Ar of the elements from sodium to aluminium

D the increase in the number of outer electrons in each atom from sodium to aluminium 16 X is the oxide of a Period 3 element. X reacts with water to give an acidic solution.

A solution is prepared by reacting 0.100 g of X with excess water. This solution was neutralised by exactly 25.0 cm3 of 0.100 mol dm–3 sodium hydroxide solution.


A Al 2O3 B MgO C P4O10 D SO3 17 Which statement about bromine is correct?

A Bromine is insoluble in non-polar solvents.

B Bromine vapour is more dense than air.

C Bromine will not vaporise significantly under normal conditions.

D Gaseous bromine is purple. 18 The addition of aqueous silver nitrate to aqueous barium chloride produces a white precipitate

which dissolves in excess dilute aqueous ammonia to form a colourless solution.

The addition of excess dilute nitric acid to the colourless solution produces a white precipitate, Z.

What is Z?

A AgCl B BaCl 2 C Ba(NO3)2 D NH4NO3

7


19 Element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statements.

Student P ‘The molecule of Y contains lone pairs of electrons.’

Student Q ‘The oxidation number of X increases by 1 from Y to Z.’

X could be carbon or nitrogen or sulfur.

Which student(s) made a correct statement?

A P only

B Q only

C both P and Q

D neither P nor Q 20 How many isomeric esters have the molecular formula C4H8O2?

A 2 B 3 C 4 D 5 21 A new jet fuel has been produced that is a mixture of different structural isomers of compound Q.

Q

Which skeletal formula represents a structural isomer of Q?

A B

C D

8

© UCLES 2015 9701/13/O/N/15

22 Crude oil is a mixture of many hydrocarbons ranging in size from 1 to 40 carbon atoms per molecule. The alkanes in crude oil can be separated because they have different boiling points.

The table below shows the boiling points of some alkanes.

alkane boiling point

/ °C Mr

butane 0 58

pentane 36 72

hexane 69 86

2-methylbutane 28 72

dimethylpropane 10 72

2,3-dimethylbutane 58 86

What is the correct explanation for the difference in the boiling points of the three isomers with Mr = 72?

A Boiling point is dependent upon the length of the carbon chain only.

B Increased branching on a carbon chain increases the boiling point.

C Increased branching reduces the strength of the intermolecular hydrogen bonding.

D Increased branching reduces the strength of the intermolecular van der Waals’ forces. 23 Compound Q contains three double bonds per molecule.

CH2 CH2CH CH2C

O O

C OHX Y

Q

Which bond, X or Y, will be ruptured by hot, concentrated acidified KMnO4 and how many lone pairs of electrons are present in one molecule of Q?

bond ruptured by hot,

concentrated acidified KMnO4 number of lone pairs

A X 5

B X 6

C Y 5

D Y 6

9


24 Which compound undergoes an SN1 substitution reaction with NaOH(aq)?

A CH3CH2CH2Br

CH2=CHCl

B (CH3)3CCH2I

C

CH3 Cl

D

25 If the starting material is iodoethane, which sequence of reactions will produce propanoic acid as

the main final product in good yield?

A add NaOH(aq), isolate the organic product, add acidified K2Cr2O7 and boil under reflux

B add NaOH(aq), isolate the organic product, add H2SO4(aq) and boil under reflux

C heat with HCN in ethanol, isolate the organic product, add H2SO4(aq) and boil under reflux

D heat with KCN in ethanol, isolate the organic product, add H2SO4(aq) and boil under reflux

26 Which compound cannot be oxidised by acidified potassium dichromate(VI) solution but does

react with sodium metal?

A (CH3)3COH

B CH3COCH2CH3

C CH3CH2CH2CH2OH

D CH3CH2CH(OH)CH3 27 Butan-2-ol can be made by reducing X with H2 / Ni.

Butan-2-ol can be dehydrated to form Y and Z which are structural isomers of each other.

Which row is correct?

X is cis-trans isomerism

is shown by

A an aldehyde both Y and Z

B an aldehyde only one of Y and Z

C a ketone both Y and Z

D a ketone only one of Y and Z

10

© UCLES 2015 9701/13/O/N/15

28 Tollens’ reagent can be used to help identify compounds P, Q and R.

C

O

P

HH3CC

O

Q

CH3

CH3

H3C

H3C

R

C

H

OH

Which compound(s) form a silver precipitate on warming with Tollens’ reagent?

A P and Q B P only C Q only D R only 29 Sorbitol is a naturally-occurring compound with a sweet taste. It is often used as a substitute for

sucrose by the food industry.

H C

H

OH

OH

OH

OH

OH

OH

H C

H C

H C

H C

H C

H

sorbitol

How many chiral centres are present in sorbitol?

A 3 B 4 C 5 D 6 30 Which compound produces butan-2-ol and ethanoic acid on hydrolysis?

A CH3CO2CH(CH3)2

B CH3CO2CH(CH3)CH2CH3

C CH3CH(CH3)CO2CH2CH3

D CH3CH2CO2CH(CH3)CH2CH3

11


Section B For each of the questions in this section, one or more of the three numbered statements 1 to 3 may be correct. Decide whether each of the statements is or is not correct (you may find it helpful to put a tick against the statements that you consider to be correct). The responses A to D should be selected on the basis of

A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 31 Which statements about orbitals in a krypton atom are correct?

1 The 1s and 2s orbitals have the same energy as each other but different sizes.

2 The third energy level (n=3) has three subshells and nine orbitals.

3 The 3d subshell has five orbitals that have the same energy as each other in an isolated atom.

32 The Group IV elements carbon, silicon and germanium can all exist in the giant molecular

structure which is also found in diamond. The bond lengths in these structures are given below.

element X C Si Ge

bond length X–X / nm 0.154 0.234 0.244

Why does the bond length increase down the group?

1 Orbital overlap decreases down the group.

2 Atomic radius increases down the group.

3 Nuclear charge increases down the group.

12

© UCLES 2015 9701/13/O/N/15


A B C D

1, 2 and 3 are

correct



1 only is

correct

No other combination of statements is used as a correct response. 33 The salt NaCl O3 is used as a non-selective weedkiller.

On careful heating, this reaction occurs: 4NaCl O3 → NaCl + 3NaCl O4.

On strong heating this reaction occurs: NaCl O4 → NaCl + 2O2.

The overall reaction is 2NaCl O3 → 2NaCl + 3O2.

What do these equations show?

1 NaCl O3 can behave as an oxidising agent.

2 NaCl O3 can behave as a reducing agent.

3 The oxidation numbers of chlorine in the three compounds shown are +6, +8 and –1. 34 Which statements correctly describe an effect of a rise in temperature on a gas-phase reaction?

1 More particles now have energies greater than the activation energy.

2 The energy distribution profile changes with more particles having the most probable energy.

3 The activation energy of the reaction is decreased. 35 Which statements concerning the Group II elements magnesium, calcium and barium are

correct?

1 Their reactivity increases with increasing relative atomic mass.

2 The oxidation number exhibited in their stable compounds is +2.

3 On strong heating, their nitrates give off oxygen only. 36 Sulfur dioxide is used as a food preservative.

Which statements about sulfur dioxide, SO2, are correct?

1 SO2 behaves as an antioxidant.

2 Aqueous SO2 contains SO32– ions.

3 SO2 inhibits the growth of mould and yeasts.

13

© UCLES 2015 9701/13/O/N/15

37 An oxidising agent that can oxidise ethanal to ethanoic acid, or to ethanoate ions, will also oxidise methanoic acid, HCO2H, to carbon dioxide and water.

Which reagents, on heating, will react differently with HCO2H and CH3CO2H?

1 Na2CO3(aq)

2 Fehling’s reagent

3 dilute acidified KMnO4 38 Each of the compounds below is treated separately with excess NaBH4. The product of each

reaction is then heated with excess concentrated H2SO4.

In each case, one or more products are formed with molecular formula C7H10.

Which compounds give only one final product with the molecular formula C7H10?

1

O

O

2

O

O

3

O

O 39 Which reactions result in the formation of propanoic acid?

1 CH3CH2CO2Na with dilute H2SO4(aq)

2 CH3CH=CHCH3 with hot, concentrated H+ / MnO4

–(aq)

3 CH3CH2OH with H+ / Cr2O7

2–(aq) 40 The diagram shows the structure of propanamide.

H

H

H

C

H

H

H O

H

C C N

propanamide

Which statements about the hydrolysis of propanamide are correct?

1 Propanamide can be hydrolysed by heating under reflux with H2SO4(aq).

2 Propanamide can be hydrolysed by heating under reflux with NaOH(aq).

3 Propanamide can be hydrolysed by cold water.

14

© UCLES 2015 9701/13/O/N/15

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15

© UCLES 2015 9701/13/O/N/15

BLANK PAGE

16

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series.


© UCLES 2015 9701/13/O/N/15

BLANK PAGE


Write your Centre number, candidate number and name on all the work you hand in.Write in dark blue or black pen.You may use an HB pencil for any diagrams or graphs.Do not use staples, paper clips, glue or correction fl uid.DO NOT WRITE IN ANY BARCODES.

Answer all questions.Electronic calculators may be used.You may lose marks if you do not show your working or if you do not use appropriate units.A Data Booklet is provided.

At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.

CHEMISTRY 9701/21

Paper 2 Structured Questions AS Core October/November 2015

1 hour 15 minutes

Candidates answer on the Question Paper.

Additional Materials: Data Booklet

Cambridge International ExaminationsCambridge International Advanced Subsidiary and Advanced Level

This document consists of 8 printed pages.

[Turn overIB15 11_9701_21/FP© UCLES 2015

*7466726655*

2

9701/21/O/N/15© UCLES 2015

Answer all the questions in the spaces provided.

1 Aluminium is a metal in Period 3 and Group III of the Periodic Table.

(a) Describe the structure of solid aluminium.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) A common use of aluminium is to make the conducting cables in long distance overhead power lines.

(i) Suggest two properties of aluminium that make it suitable for this use.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

The cables are attached to pylons by ceramic supports.

(ii) Describe the structure of a ceramic material.

.............................................................................................................................................

....................................................................................................................................... [1]

(iii) State the property of a ceramic material that makes it suitable for this use.

.............................................................................................................................................

....................................................................................................................................... [1]

3

9701/21/O/N/15© UCLES 2015 [Turn over

(c) Aluminium reacts with chlorine to form a white, solid chloride that contains 79.7% chlorine and sublimes (changes straight from a solid to a gas) at 180 °C.

(i) Describe the structure and bonding in this compound. Suggest how it explains the low sublimation temperature.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Calculate the empirical formula of the chloride. You must show your working.

empirical formula = .............................. [2]

At 200 °C and 100 kPa, a 1.36 g sample of this chloride occupied a volume of 200 cm3.

(iii) Calculate the relative molecular mass, Mr, of the chloride. Give your answer to three signifi cant fi gures.

Mr = .............................. [2]

(iv) Deduce the molecular formula of this chloride at 200 °C.

....................................................................................................................................... [1]

[Total: 13]

4

9701/21/O/N/15© UCLES 2015

2 (a) (i) Explain the meaning of the term enthalpy change of formation.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Give the equation for the reaction for which the enthalpy change corresponds to the standard enthalpy change of formation of liquid sulfur trioxide, SO3. Include state symbols.

....................................................................................................................................... [1]

(b) Ammonia is manufactured by the Haber process.

N2(g) + 3H2(g) 2NH3(g)

(i) Use bond energies from the Data Booklet to calculate the enthalpy change of reaction for the Haber process. Include a sign in your answer.

enthalpy change .............................. kJ mol–1 [3]

(ii) State the essential operating conditions for the Haber process.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(iii) Explain the choices of temperature and pressure for the Haber process.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [4]

5


(c) One of the major uses of ammonia is in the manufacture of fertilisers such as diammonium hydrogen phosphate, (NH4)2HPO4.

(i) Write an equation for the formation of diammonium hydrogen phosphate by the reaction between ammonia and phosphoric acid, H3PO4.

....................................................................................................................................... [1]

(ii) Explain this reaction in terms of the Brønsted-Lowry theory.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(d) The use of nitrate fertilisers can give rise to environmental consequences in terms of effects on both rivers and the atmosphere.

(i) Explain how the uncontrolled use of nitrate fertilisers can result in a severe reduction in water quality in rivers.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) Oxides of nitrogen are produced by the action of bacteria on nitrate fertilisers.

Explain the problems associated with the release of oxides of nitrogen into the atmosphere. Include an equation in your answer.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

[Total: 21]

6

9701/21/O/N/15© UCLES 2015

3 Heptane, C7H16, is an undesirable component of petrol as it burns explosively causing ‘knocking’ in an engine.

(a) There are nine structural isomers with the formula C7H16, only two of which contain chiral centres.

(i) Explain the meanings of the terms structural isomers and chiral.

structural isomers ...............................................................................................................

.............................................................................................................................................

.............................................................................................................................................

chiral ...................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

(ii) Give the structures and names of the two structural isomers of C7H16 which contain a chiral centre.

[4]

(b) (i) Write an equation for the complete combustion of heptane.

....................................................................................................................................... [1]

(ii) Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant.

....................................................................................................................................... [1]

(iii) Incomplete combustion can also lead to emission of unburnt hydrocarbons.

State one environmental consequence of this.

....................................................................................................................................... [1]

7


(c) The reaction of heptane with chlorine in the presence of UV light produces a wide variety of products.

Formation of the monochloroheptanes can be represented by the following equation.

C7H16 + Cl 2 → C7H15Cl + HCl

(i) Name the mechanism of the reaction between heptane and chlorine in the presence ofUV light.

....................................................................................................................................... [1]

(ii) Describe this mechanism, using suitable equations and including the names of each stage in the process.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [5]

[Total: 15]

8

9701/21/O/N/15© UCLES 2015

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity.

To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series.


4 Some reactions involving ethanol are shown.

CH3CH2Cl CH3CH2OH Y

X

distil withCr2O7

2– + H+

reaction 1

reaction 2heat with NaOH

in ethanol

(a) (i) Give an equation for reaction 2 including the reagent needed for the conversion.

....................................................................................................................................... [2]

(ii) State the reagent and conditions required for reaction 1.

....................................................................................................................................... [2]

(b) (i) Identify the organic product X.

....................................................................................................................................... [1]

(ii) Nitric acid is added to the products of reaction of CH3CH2Cl with NaOH in ethanol. Silver nitrate solution is then added to this mixture.

State what you would observe.

....................................................................................................................................... [1]

(iii) Write an ionic equation, including state symbols, for the reaction responsible for the observation in (ii).

....................................................................................................................................... [1]

(c) (i) Identify the organic product Y which is distilled out of the reaction mixture.

....................................................................................................................................... [1]

(ii) Explain, in terms of the properties of and intermolecular forces in CH3CH2OH and Y, why the chosen conditions for the reaction ensure that Y is the product.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

[Total: 11]





CHEMISTRY 9701/22


1 hour 15 minutes





[Turn overIB15 11_9701_22/4RP© UCLES 2015

*6002972519*

2

9701/22/O/N/15© UCLES 2015


1 (a) Fill the gaps in the table for each of the given particles.

nameof isotope

typeof particle charge symbol electron

confi guration

carbon-13 1s22s22p2

–1 Cl3717

–

sulfur-34 atom 0

iron-54 cation 1s22s22p63s23p63d6

[5]

(b) One of the factors that determines the type of bonding present between the particles of a substance is the relative electronegativities of the bonded particles.

(i) Explain the meaning of the term electronegativity.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Name and describe the type of bonding you would expect to fi nd between particles with equal electronegativities.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(iii) Name and describe the type of bonding you would expect to fi nd between particles with very different electronegativities.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

3


(c) The boiling points of some molecules with equal numbers of electrons are given.

substance fl uorine argon hydrogenchloride methanol

formula F2 Ar HCl CH3OH

boiling point / K 85 87 188 338

(i) Explain why the boiling points of fl uorine and argon are so similar.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Explain why the boiling point of hydrogen chloride is higher than that of fl uorine.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(iii) Explain why methanol has the highest boiling point of all these molecules.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

[Total: 17]

4

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2 Chemical reactions are accompanied by enthalpy changes.

(a) Explain the meaning of the term standard enthalpy change of reaction.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) The enthalpy change of hydration of anhydrous magnesium sulfate, ∆Hhyd MgSO4, can be calculated by carrying out two separate experiments.

In the fi rst experiment 45.00 g of water was weighed into a polystyrene cup and 3.01 g of MgSO4 was added and stirred until it was completely dissolved. The temperature of the water rose from 23.4 °C to 34.7 °C.

(i) Calculate the amount of heat energy transferred to the water during this dissolving process.

You can assume that the specifi c heat capacity of the solution is the same as that of water, 4.18 J g–1 K–1.

heat energy = .......................... J [1]

(ii) Calculate the amount, in moles, of MgSO4 dissolved.

amount = .......................... mol [1]

5


(iii) Calculate the enthalpy change of solution, ∆Hsoln, of MgSO4(s).

You must include a sign with your answer.

∆Hsoln, of MgSO4(s) = .......................... kJ mol–1 [1]

In the second experiment, the enthalpy change of solution for the hydrated salt, MgSO4.7H2O(s), was calculated and found to be +9.60 kJ mol–1.

(iv) Use the equation below for the hydration of anhydrous magnesium sulfate to construct a suitable, fully labelled energy cycle that will allow you to calculate the enthalpy change for this reaction, ∆Hhyd MgSO4.

MgSO4(s) + 7H2O(l) → MgSO4.7H2O(s)

[1]

(v) Calculate the enthalpy change for this reaction, ∆Hhyd MgSO4. Include a sign in your answer.

∆Hhyd MgSO4 = .......................... kJ mol–1 [1]

[Total: 7]

6

9701/22/O/N/15© UCLES 2015

3 The elements in Period 3, Na, Mg, Al, P and S, all react with oxygen when heated in air.

(a) (i) Give the formula of the oxide formed when each element is heated in air. One has been completed for you.

Na = ..................... Mg = ..................... Al = Al 2O3

P = ..................... S = .....................[2]

(ii) Describe what you would see when sodium and sulfur are each heated separately in air and give an equation for each reaction.

Na .......................................................................................................................................

equation ..............................................................................................................................

S .........................................................................................................................................

equation ..............................................................................................................................[4]

(b) The oxides show variations in their behaviour when added to water, acids and alkalis.

(i) Place the symbols of the elements in (a)(i) in the appropriate row of the table to indicate this behaviour.

acidic

amphoteric

basic

[2]

(ii) State the bonding present in acidic and basic oxides.

acidic ..................................................................................................................................

basic ...................................................................................................................................[2]

(iii) Write equations for the reaction of aluminium oxide with each of hydrochloric acid, HCl, and sodium hydroxide, NaOH.

with HCl ..............................................................................................................................

with NaOH ..........................................................................................................................[2]

(c) Explain how the presence of an impurity in carbonaceous fuels can give rise to acid rain.

name of impurity ........................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 14]

7

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BLANK PAGE

[Turn over

8

9701/22/O/N/15© UCLES 2015

4 Halogenoalkanes are useful intermediates in the synthesis of a wide variety of compounds.

(a) 2-bromobutane reacts in two different ways with sodium hydroxide depending on the conditions.

When warmed with aqueous sodium hydroxide, 2-bromobutane produces an alcohol that exists as a pair of optical isomers.

(i) Give the name of the mechanism of the reaction between 2-bromobutane and aqueous sodium hydroxide.

....................................................................................................................................... [1]

(ii) Explain why the alcohol produced exists as a pair of optical isomers.

.............................................................................................................................................

....................................................................................................................................... [1]

(iii) Draw the three-dimensional structure of the two optical isomers of the alcohol produced in (ii).

[2]

Heating 2-bromobutane with ethanolic sodium hydroxide produces a mixture of three alkenes, two of which are a pair of geometrical isomers.

(iv) Give the name of the mechanism of the reaction between 2-bromobutane and ethanolic sodium hydroxide.

....................................................................................................................................... [1]

9


(v) Draw and name the structures of the pair of geometrical isomers formed by reaction of 2-bromobutane with ethanolic sodium hydroxide.

name .............................................................

name .............................................................[2]

(vi) Name the third alkene produced by reaction of 2-bromobutane with ethanolic sodium hydroxide and explain why it does not show geometrical isomerism.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

10

9701/22/O/N/15© UCLES 2015

(b) Some reactions involving 2-bromopropane are shown.

CH3CHBrCH32-bromopropane

CH3CH2CO2H(and CH3CH(NH2)CH3

which is removed)

CH3CH2CH2OH

CH3CH(NH2)CH3 X

Y

reaction 1 reaction 2

reaction 5 reaction 4

reaction 3hydrolysisreaction 6

HBr

(i) State the reagent needed for reaction 1.

....................................................................................................................................... [1]

(ii) State the reagent needed for reaction 2.

....................................................................................................................................... [1]

(iii) Give the structural formula of X.

[1]

(iv) Name the type of reaction involved in reaction 4 and suggest a suitable reagent.

.............................................................................................................................................

....................................................................................................................................... [2]

(v) State the name of a solid catalyst for reaction 5.

....................................................................................................................................... [1]

11


(vi) Complete the mechanism for the production of 2-bromopropane from Y in reaction 6 shown below.

Include the structure of Y and any necessary lone pairs, curly arrows, charges and partial charges.

Y

H

Br

intermediate

H3C CH3C

H

Br

[4]

(vii) Give the name of the mechanism in (vi).

....................................................................................................................................... [1]

(viii) 1-bromopropane is a minor product of reaction 6.

Explain why 2-bromopropane is the major product of reaction 6.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

[Total: 22]

12

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BLANK PAGE








CHEMISTRY 9701/23


1 hour 15 minutes






*2045634785*

2

9701/23/O/N/15© UCLES 2015


1 Aluminium is a metal in Period 3 and Group III of the Periodic Table.

(a) Describe the structure of solid aluminium.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) A common use of aluminium is to make the conducting cables in long distance overhead power lines.

(i) Suggest two properties of aluminium that make it suitable for this use.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

The cables are attached to pylons by ceramic supports.

(ii) Describe the structure of a ceramic material.

.............................................................................................................................................

....................................................................................................................................... [1]

(iii) State the property of a ceramic material that makes it suitable for this use.

.............................................................................................................................................

....................................................................................................................................... [1]

3


(c) Aluminium reacts with chlorine to form a white, solid chloride that contains 79.7% chlorine and sublimes (changes straight from a solid to a gas) at 180 °C.

(i) Describe the structure and bonding in this compound. Suggest how it explains the low sublimation temperature.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Calculate the empirical formula of the chloride. You must show your working.

empirical formula = .............................. [2]

At 200 °C and 100 kPa, a 1.36 g sample of this chloride occupied a volume of 200 cm3.

(iii) Calculate the relative molecular mass, Mr, of the chloride. Give your answer to three signifi cant fi gures.

Mr = .............................. [2]

(iv) Deduce the molecular formula of this chloride at 200 °C.

....................................................................................................................................... [1]

[Total: 13]

4

9701/23/O/N/15© UCLES 2015

2 (a) (i) Explain the meaning of the term enthalpy change of formation.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Give the equation for the reaction for which the enthalpy change corresponds to the standard enthalpy change of formation of liquid sulfur trioxide, SO3. Include state symbols.

....................................................................................................................................... [1]

(b) Ammonia is manufactured by the Haber process.

N2(g) + 3H2(g) 2NH3(g)

(i) Use bond energies from the Data Booklet to calculate the enthalpy change of reaction for the Haber process. Include a sign in your answer.

enthalpy change .............................. kJ mol–1 [3]

(ii) State the essential operating conditions for the Haber process.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(iii) Explain the choices of temperature and pressure for the Haber process.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [4]

5


(c) One of the major uses of ammonia is in the manufacture of fertilisers such as diammonium hydrogen phosphate, (NH4)2HPO4.

(i) Write an equation for the formation of diammonium hydrogen phosphate by the reaction between ammonia and phosphoric acid, H3PO4.

....................................................................................................................................... [1]

(ii) Explain this reaction in terms of the Brønsted-Lowry theory.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(d) The use of nitrate fertilisers can give rise to environmental consequences in terms of effects on both rivers and the atmosphere.

(i) Explain how the uncontrolled use of nitrate fertilisers can result in a severe reduction in water quality in rivers.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) Oxides of nitrogen are produced by the action of bacteria on nitrate fertilisers.

Explain the problems associated with the release of oxides of nitrogen into the atmosphere. Include an equation in your answer.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

[Total: 21]

6

9701/23/O/N/15© UCLES 2015

3 Heptane, C7H16, is an undesirable component of petrol as it burns explosively causing ‘knocking’ in an engine.

(a) There are nine structural isomers with the formula C7H16, only two of which contain chiral centres.

(i) Explain the meanings of the terms structural isomers and chiral.

structural isomers ...............................................................................................................

.............................................................................................................................................

.............................................................................................................................................

chiral ...................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

(ii) Give the structures and names of the two structural isomers of C7H16 which contain a chiral centre.

[4]

(b) (i) Write an equation for the complete combustion of heptane.

....................................................................................................................................... [1]

(ii) Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant.

....................................................................................................................................... [1]

(iii) Incomplete combustion can also lead to emission of unburnt hydrocarbons.

State one environmental consequence of this.

....................................................................................................................................... [1]

7


(c) The reaction of heptane with chlorine in the presence of UV light produces a wide variety of products.

Formation of the monochloroheptanes can be represented by the following equation.

C7H16 + Cl 2 → C7H15Cl + HCl

(i) Name the mechanism of the reaction between heptane and chlorine in the presence ofUV light.

....................................................................................................................................... [1]

(ii) Describe this mechanism, using suitable equations and including the names of each stage in the process.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [5]

[Total: 15]

8

9701/23/O/N/15© UCLES 2015




4 Some reactions involving ethanol are shown.

CH3CH2Cl CH3CH2OH Y

X

distil withCr2O7

2– + H+

reaction 1

reaction 2heat with NaOH

in ethanol

(a) (i) Give an equation for reaction 2 including the reagent needed for the conversion.

....................................................................................................................................... [2]

(ii) State the reagent and conditions required for reaction 1.

....................................................................................................................................... [2]

(b) (i) Identify the organic product X.

....................................................................................................................................... [1]

(ii) Nitric acid is added to the products of reaction of CH3CH2Cl with NaOH in ethanol. Silver nitrate solution is then added to this mixture.

State what you would observe.

....................................................................................................................................... [1]

(iii) Write an ionic equation, including state symbols, for the reaction responsible for the observation in (ii).

....................................................................................................................................... [1]

(c) (i) Identify the organic product Y which is distilled out of the reaction mixture.

....................................................................................................................................... [1]

(ii) Explain, in terms of the properties of and intermolecular forces in CH3CH2OH and Y, why the chosen conditions for the reaction ensure that Y is the product.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

[Total: 11]


Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen.You may use an HB pencil for any diagrams or graphs.Do not use staples, paper clips, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.

Answer all questions.Electronic calculators may be used.You may lose marks if you do not show your working or if you do not use appropriate units.Use of a Data Booklet is unnecessary.A copy of the Periodic Table is printed on page 12.

Qualitative Analysis Notes are printed on pages 10 and 11.


CHEMISTRY 9701/31

Paper 3 Advanced Practical Skills 1 October/November 2015

2 hours


Additional Materials: As listed in the Confidential Instructions


This document consists of 12 printed pages and 1 insert.


*9899326369*

Session

Laboratory

For Examiner’s Use

1

2

3

Total

2

9701/31/O/N/15© UCLES 2015

1 In this experiment you will determine the ionic equation for the reaction of acidified potassium manganate(VII) with potassium iodide. Excess potassium iodide is used and the reaction produces iodine. The amount of iodine produced is measured by titration with sodium thiosulfate.

FA 1 is 0.0180 mol dm–3 potassium manganate(VII), KMnO4. FA 2 is 1.00 mol dm–3 sulfuric acid, H2SO4. FA 3 is 0.500 mol dm–3 potassium iodide, KI. FA 4 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. starch indicator

(a) Method

● Pipette 25.0 cm3 of FA 1 into a conical flask. ● Use the measuring cylinder to add 25 cm3 of FA 2 to the conical flask. ● Use the measuring cylinder to add 20 cm3 of FA 3 to the conical flask. ● Fill the burette with FA 4. ● Carry out a rough titration. When the colour of the mixture becomes yellow/orange, add a

few drops of starch indicator. Then titrate until the mixture goes colourless. ● Record all your burette readings in the space below.

The rough titre is ........................ cm3.

● Carry out as many accurate titrations as you think necessary to obtain consistent results. ● Make sure any recorded results show the precision of your practical work. ● Record in a suitable form below all of your burette readings and the volume of FA 4 added

in each accurate titration.

Keep FA 1 and FA 2 for use in Question 3 and FA 4 for use in Question 2.

[7]

(b) From your accurate titration results, obtain a suitable value for the volume of FA 4 to be used in your calculations.

Show clearly how you have obtained this value.

Volume of FA 4 required is ..................... cm3. [1]

I

II

III

IV

V

VI

VII

3


(c) Calculations

Show your working and appropriate significant figures in the final answer to each step of your calculations.

(i) Calculate the number of moles of sodium thiosulfate in the volume of FA 4 calculatedin (b).

moles of Na2S2O3 = ............................. mol

(ii) Use the equation below to calculate the number of moles of iodine that reacted with the sodium thiosulfate in the titration.

I2 + 2Na2S2O3 → Na2S4O6 + 2NaI

moles of I2 = ............................. mol

(iii) Use information on page 2 to calculate the number of moles of potassium manganate(VII) in FA 1 used in the titration.

moles of KMnO4 = ............................. mol

(iv) From your answers to (ii) and (iii), calculate the number of moles of iodine produced by the reaction of 2.00 moles of potassium manganate(VII) with excess potassium iodide.

moles I2 = ............................. mol

(v) Using your answer to (iv), put a tick next to the ionic equation that represents the reaction between FA 1 and FA 3.

2MnO4– + 2I– + 16H+ → I2 + 2Mn6+ + 8H2O ...........

2MnO4– + 4I– + 16H+ → 2I2 + 2Mn5+ + 8H2O ...........

2MnO4– + 6I– + 16H+ → 3I2 + 2Mn4+ + 8H2O ...........

2MnO4– + 8I– + 16H+ → 4I2 + 2Mn3+ + 8H2O ...........

2MnO4– + 10I– + 16H+ → 5I2 + 2Mn2+ + 8H2O ...........

2MnO4– + 12I– + 16H+ → 6I2 + 2Mn+ + 8H2O ...........

4

9701/31/O/N/15© UCLES 2015

(vi) Prove that the iodide ion has been oxidised in the equation that you selected in (v).

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[5]

(d) (i) The error in calibration of the pipette you used is ±0.06 cm3. Calculate the percentage error when measuring FA 1, using the pipette.

percentage error = ..................... %

(ii) A student suggested that the experiment would be more accurate if a pipette was used to measure solution FA 3.

State and explain whether you agree with the student.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

[Total: 15]

5


2 In this experiment you will investigate how the rate of reaction between sodium thiosulfate and hydrochloric acid is affected by the concentration of the acid.

When aqueous thiosulfate ions react with hydrogen ions, H+, in any acid, a pale yellow precipitate of sulfur is formed. The ionic equation for this reaction is given below.

S2O32–(aq) + 2H+(aq) → S(s) + SO2(aq) + H2O(l)

The rate of the reaction can be determined by measuring the time taken to produce a fixed quantity of sulfur.

FA 4 is 0.10 mol dm–3 sodium thiosulfate, Na2S2O3. FA 5 is 0.20 mol dm–3 hydrochloric acid, HCl.

(a) Method

Record all your measurements, in an appropriate form, in the space below.

Experiment 1

● Use the larger measuring cylinder to transfer 40 cm3 of FA 4 into the 100 cm3 beaker. ● Rinse the larger measuring cylinder thoroughly with water, then add 30 cm3 of FA 5 to the

beaker and start timing immediately. ● Stir the mixture once and place the beaker on top of the printed insert page provided. ● Look down through the solution in the beaker at the print on the insert. ● Stop timing as soon as the precipitate of sulfur makes the print on the insert invisible. ● Record the reaction time to the nearest second. ● Empty and rinse the 100 cm3 beaker. ● Dry the outside of the beaker ready for Experiment 2.

Experiment 2

● Rinse the larger measuring cylinder, then use it to transfer 40 cm3 of FA 4 into the 100 cm3 beaker.

● Use the smaller measuring cylinder to add 10 cm3 of distilled water to the beaker. ● Use the same measuring cylinder to add 20 cm3 of FA 5 to the mixture in the beaker and

start timing immediately. ● Stir the mixture once and place the beaker on top of the printed insert page provided. ● Stop timing as soon as the print on the insert becomes invisible. ● Record the reaction time to the nearest second. ● Empty and rinse the 100 cm3 beaker. ● Dry the outside of the beaker ready for Experiment 3.

Experiment 3

● Carry out the reaction using a mixture of 40 cm3 of FA 4, 20 cm3 of distilled water and 10 cm3 of FA 5.

● Measure and record the reaction time to the nearest second.

[4]

I

II

III

IV

6

9701/31/O/N/15© UCLES 2015

(b) (i) The ‘rate of reaction’ can be represented by the formula below.

‘rate of reaction’ = reaction time1000

Use this formula to calculate the ‘rate of reaction’ for Experiments 1 and 3. Give the unit.

‘rate of reaction’ for Experiment 1 ............................ unit ..............


(ii) Calculate the initial concentrations of hydrochloric acid in the reaction mixtures in Experiments 1 and 3.

initial concentration of HCl in Experiment 1 = ............................. mol dm–3


(iii) How is the ‘rate of reaction’ affected by the concentration of hydrochloric acid in the mixture?

.............................................................................................................................................

.............................................................................................................................................

(iv) Predict how the reaction time measured in Experiment 1 would have been affected if the experiment had been carried out using 0.20 mol dm–3 sulfuric acid instead of 0.20 mol dm–3 hydrochloric acid.

Explain your answer.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(v) Predict how the reaction time measured in Experiment 3 would have been affected if the experiment had been carried out in a 250 cm3 beaker instead of a 100 cm3 beaker.


.............................................................................................................................................

.............................................................................................................................................[5]

[Total: 9]

7


3 Qualitative Analysis

At each stage of any test you are to record details of the following.

● colour changes seen ● the formation of any precipitate ● the solubility of such precipitates in an excess of the reagent added

Where gases are released they should be identified by a test, described in the appropriate place in your observations.

You should indicate clearly at what stage in a test a change occurs. No additional tests for ions present should be attempted.

If any solution is warmed, a boiling tube MUST be used.

Rinse and reuse test-tubes and boiling tubes where possible.

Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given.

(a) FA 6 is a sodium compound containing one anion listed on page 11.

Dissolve the FA 6 provided in about 15 cm3 of distilled water in a boiling tube. Carry out the following tests and record your observations in the table below.

test observations (i) To a 1cm depth of the solution

of FA 6 in a test-tube, add a few drops of aqueous barium chloride or aqueous barium nitrate, then

add dilute hydrochloric acid.

(ii) To a 1cm depth of the solution of FA 6 in a test-tube, add an equal volume of aqueous hydrogen peroxide, then

add a few drops of aqueous barium chloride or aqueous barium nitrate, then


8

9701/31/O/N/15© UCLES 2015

test observations (iii) To a 1 cm depth of the solution

of FA 6 in a boiling tube, add an equal volume of FA 2, sulfuric acid, then

heat the mixture gently and cautiously.

(iv) To a 1 cm depth of the solution of FA 6 in a test-tube, add an equal volume of aqueous sodium hydroxide, then

add a few drops of FA 1, aqueous potassium manganate(VII), then

add FA 2, sulfuric acid.

(v) Identify the anion in FA 6, and state one piece of evidence for your identification.

anion ...............................................

evidence .............................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(vi) Give the chemical equation for the reaction between FA 6 and hydrogen peroxide, H2O2, in test (ii). State symbols are not required.

.............................................................................................................................................[7]

9


(b) FA 7, FA 8, FA 9 and FA 10 each contain one cation from the list on page 10. You will attempt to identify the cations by testing with aqueous sodium hydroxide and aqueous

ammonia. In each case, use a 1 cm depth of the solution in a test-tube.

(i) Complete the table below.

testobservations

FA 7 FA 8 FA 9 FA 10

add sodiumhydroxide

add aqueousammonia

(ii) Use your observations to identify, as far as possible, the cation present in each solution. If alternative identities are possible, state this clearly.

FA 7 cation ....................................................

FA 8 cation ....................................................

FA 9 cation ....................................................

FA 10 cation ..................................................

(iii) Give the ionic equation for the reaction of one of your cations with a few drops of sodium hydroxide. State symbols are not required.

.............................................................................................................................................

(iv) The precipitates obtained when alkalis are added to solutions of certain cations are sometimes difficult to see. Suggest how, using no additional apparatus, the experiment could be repeated in a way that would make these precipitates more visible.

.............................................................................................................................................

.............................................................................................................................................[9]

[Total: 16]

10

9701/31/O/N/15© UCLES 2015

Qualitative Analysis Notes

Key: [ppt. = precipitate]

1 Reactions of aqueous cations

ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al

3+(aq)white ppt.soluble in excess

white ppt.insoluble in excess

ammonium,NH4

+(aq)no ppt.ammonia produced on heating

–

barium,Ba2+(aq)

no ppt. (if reagents are pure) no ppt.

calcium,Ca2+(aq)

white ppt. with high [Ca2+(aq)] no ppt.

chromium(III),Cr3+(aq)

grey-green ppt. soluble in excessgiving dark green solution

grey-green ppt.insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.insoluble in excess

blue ppt. soluble in excessgiving dark blue solution

iron(II),Fe2+(aq)

green ppt. turning brown on contact with airinsoluble in excess


iron(III),Fe3+(aq)

red-brown ppt.insoluble in excess


magnesium,Mg2+(aq)



manganese(II),Mn2+(aq)

off-white ppt. rapidly turning brownon contact with airinsoluble in excess


zinc,Zn2+(aq)

white ppt.soluble in excess


11

9701/31/O/N/15© UCLES 2015

2 Reactions of anions

ion reaction

carbonate,CO3

2–

CO2 liberated by dilute acids

chloride,Cl

–(aq)gives white ppt. with Ag+(aq) (soluble in NH3(aq))

bromide,Br

–(aq)gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq))

iodide,I

–(aq)gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq))

nitrate,NO3

–(aq)NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO2

–(aq)

NH3 liberated on heating with OH–(aq) and Al foil;NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulfate,SO4

2–(aq)gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids)

sulfite,SO3

2–(aq)SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases

gas test and test result

ammonia, NH3 turns damp red litmus paper blue

carbon dioxide, CO2 gives a white ppt. with limewater(ppt. dissolves with excess CO2)

chlorine, Cl 2 bleaches damp litmus paper

hydrogen, H2 “pops” with a lighted splint

oxygen, O2 relights a glowing splint

sulfur dioxide, SO2turns acidified aqueous potassium manganate(VII) from purple to colourless

12

9701/31/O/N/15© UCLES 2015


Gro

up

140

Ce

Cer

ium

58

141

PrP

rase

odym

ium

59

144

Nd

Neo

dym

ium

60

PmP

rom

ethi

um61

150

SmS

amar

ium

62

152

EuE

urop

ium

63

157

Gd

Gad

olin

ium

64

159

Tb Terb

ium

65

163

Dy

Dys

pros

ium

66

165

Ho

Hol

miu

m67

167

Er Erb

ium

68

169

Tm Thul

ium

69

173

YbY

tterb

ium

70

175

LuLu

tetiu

m71

Th Thor

ium

90

PaP

rota

ctin

ium

91

UU

rani

um92

Np

Nep

tuni

um93

PuP

luto

nium

94

Am

Am

eric

ium

95

Cm

Cur

ium

96

Bk

Ber

keliu

m97

Cf

Cal

iforn

ium

98

EsE

inst

eini

um99

Fm Ferm

ium

100

Md

Men

dele

vium

101

No

Nob

eliu

m10

2

LrLa

wre

nciu

m10

3

1.0 H

Hyd

roge

n1

6.9 Li

Lith

ium

3

23.0

Na

Sod

ium

11

24.3

Mg

Mag

nesi

um12

40.1

Ca

Cal

cium

20

45.0 Sc

Sca

ndiu

m21

47.9 Ti

Tita

nium

22

50.9 V

Vana

dium

23

52.0 Cr

Chr

omiu

m24

54.9

Mn

Man

gane

se25

55.8 Fe Iron

26

58.9

Co

Cob

alt

27

58.7 Ni

Nic

kel

28

63.5

Cu

Cop

per

29

65.4

Zn Zinc

30

69.7

Ga

Gal

lium

31

27.0 Al

Alu

min

ium

13

10.8 B B

oron

5

12.0 C

Car

bon

6

14.0 N

Nitr

ogen

7

16.0 O

Oxy

gen

8

19.0 F

Fluo

rine

9

28.1 Si S

ilico

n14

31.0 P

Pho

spho

rus

15

32.1 S S

ulfu

r16

35.5 Cl

Chl

orin

e17

39.9 Ar

Arg

on18

20.2 Ne

Neo

n10

4.0

He

Hel

ium

2

72.6

Ge

Ger

man

ium

32

74.9

As

Ars

enic

33

79.0 Se

Sel

eniu

m34

79.9 Br

Bro

min

e35

83.8 Kr

Kry

pton

36

39.1 K

Pot

assi

um19

87.6 Sr

Stro

ntiu

m38

88.9 Y

Yttr

ium

39

91.2 Zr

Zirc

oniu

m40

92.9

Nb

Nio

bium

41

95.9

Mo

Mol

ybde

num

42

TcTe

chne

tium

43

101

Ru

Rut

heni

um44

103

Rh

Rho

dium

45

106

PdP

alla

dium

46

108

Ag

Silv

er47

112

Cd

Cad

miu

m48

115

In Indi

um49

119

Sn Tin

50

122

SbA

ntim

ony

51

128

TeTe

lluriu

m52

127 I

Iodi

ne53

131

Xe Xen

on54

137

Ba

Bar

ium

56

139

LaLa

ntha

num

57

*

178

Hf

Haf

nium

72

181

TaTa

ntal

um73

184 W

Tung

sten

74

186

Re

Rhe

nium

75

190

Os

Osm

ium

76

192

Ir Iridi

um77

195 Pt

Pla

tinum

78

197

Au

Gol

d79

201

Hg

Mer

cury

80

204 Tl

Thal

lium

81

207

Pb Lead

82

209 Bi

Bis

mut

h83

PoP

olon

ium

84

At

Ast

atin

e85

Rn

Rad

on86

Rf

Rut

herfo

rdiu

m10

4

Db

Dub

nium

105

SgS

eabo

rgiu

m10

6

Bh

Boh

rium

107

Hs

Has

sium

108

Mt

Mei

tner

ium

109

Uun

Unu

nnili

um11

0

Uuu

Unu

nuni

um11

1

Uub

Unu

nbiu

m11

2

Uuq

Unu

nqua

dium

114

Uuh

Unu

nhex

ium

116

Uuo

Unu

noct

ium

118

FrFr

anci

um87

Ac

Act

iniu

m89

9.0

Be

Ber

ylliu

m4

III

IIIIV

VV

IV

II0

85.5

Rb

Rub

idiu

m37

133

Cs

Cae

sium

55

Ra

Rad

ium

88 a Xb

a =

rela

tive

atom

ic m

ass

X =

atom

ic s

ymbo

l

b =

prot

on (a

tom

ic) n

umbe

r

Key

* 58-

71 L

anth

anid

es90

-103

Act

inid

es

The

Perio

dic

Tabl

e of

the

Elem

ents

*


Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen.You may use an HB pencil for any diagrams or graphs.Do not use staples, paper clips, glue or correction fl uid.DO NOT WRITE IN ANY BARCODES.

Answer all questions.Electronic calculators may be used.You may lose marks if you do not show your working or if you do not use appropriate units.Use of a Data Booklet is unnecessary.

Qualitative Analysis Notes are printed on pages 10 and 11.A Periodic Table is printed on page 12.


CHEMISTRY 9701/33


2 hours


Additional Materials: As listed in the Confi dential Instructions




*3461274007*

Session

Laboratory


1

2

3

Total

2

9701/33/O/N/15© UCLES 2015

1 The formula of hydrated copper(II) sulfate is CuSO4.xH2O where x is the number of moles of water of crystallisation in one mole of salt. You will determine the value of x by titration.

When aqueous copper(II) ions react with aqueous iodide ions, I–, iodine is produced.

2Cu2+(aq) + 4I–(aq) → I2(aq) + 2CuI(s)

The amount of iodine, I2, produced can be found by titrating it with aqueous thiosulfate ions, S2O32–.

2S2O32–(aq) + I2(aq) → S4O6

2–(aq) + 2I–(aq)

FA 1 is aqueous CuSO4.xH2O containing 26.2 g dm–3. FA 2 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. FA 3 is aqueous potassium iodide, KI. starch indicator

(a) Method

● Pipette 25.0 cm3 of FA 1 into a conical flask. ● Use the measuring cylinder to add 15 cm3 of FA 3, an excess of KI, to the conical flask.

The solution will turn brown because iodine is formed. ● Fill the burette with FA 2. ● Add FA 2 from the burette until the colour of the mixture changes to pale brown. ● Add 10 drops of starch indicator. The mixture will turn blue-black. ● Continue adding FA 2 from the burette until the dark colour suddenly disappears to leave

an off-white solid. This is the end point of the titration. ● Carry out a rough titration and record your burette readings in the space below.

The rough titre is ............................. cm3.

● Carry out as many accurate titrations as you think necessary to obtain consistent results. ● Make certain any recorded results show the precision of your practical work. ● Record in a suitable form below, all your burette readings and the volume of FA 2 added


[7]

I

II

III

IV

V

VI

VII

3


(b) From your accurate titration results, obtain a suitable value to be used in your calculations. Show clearly how you have obtained this value.

25.0 cm3 of FA 1 required ............................. cm3 of FA 2. [1]

(c) Calculations

Show your working and appropriate signifi cant fi gures in each step of your calculations.

(i) Calculate the number of moles of thiosulfate ions present in the volume of FA 2 you have calculated in (b).

moles of S2O32– = ............................. mol

(ii) Use your answer to (i), and the equations for the reactions involved, to deduce the number of moles of Cu2+ present in 25.0 cm3 of FA 1.

2Cu2+(aq) + 4I–(aq) → I2(aq) + 2CuI(s)

2S2O32–(aq) + I2(aq) → S4O6

2– (aq) + 2I–(aq)

moles of Cu2+ = ............................. mol

(iii) Use your answer to (ii) and the mass of CuSO4.xH2O present in the solution, to calculate the relative molecular mass, Mr, of CuSO4.xH2O.

Mr of CuSO4.xH2O = .............................

(iv) Determine the value of x. (Use data from the Periodic Table on page 12.)

x = .............................[6]

[Total: 14]

4

9701/33/O/N/15© UCLES 2015

2 FA 4 is an impure sample of hydrated calcium chloride, CaCl 2.2H2O. On heating, hydrated calcium chloride loses its water of crystallisation.

CaCl 2.2H2O(s) → CaCl 2(s) + 2H2O(g)

You will determine the purity of FA 4 by measuring the loss in mass that occurs when it is heated. The impurity present in FA 4 is not decomposed on heating.

(a) Method

You should read the instructions carefully before starting any practical work and draw a table for your results in the space below.

● Weigh a crucible and record its mass. ● Add between 1.80 g and 2.00 g of FA 4 into the crucible. ● Reweigh the crucible and its contents and record the mass. ● Place the crucible on the pipe-clay triangle and heat gently for 1 minute and then strongly

for a further 2 minutes. ● Allow the crucible and its contents to cool. Reweigh the crucible and contents and record

the mass. ● Heat the crucible strongly for a further 2 minutes. Allow it to cool. Reweigh the crucible and

contents and record the mass. ● Repeat the heating, cooling and weighing until you are satisfied that all the water of

crystallisation has been removed. ● Calculate and record the mass of FA 4 used and the total mass of water lost.

While you are waiting for the crucible to cool, you may wish to start work on Question 3.

[6]

I

II

III

IV

V

VI

5


(b) Calculations

Show your working and appropriate signifi cant fi gures in the fi nal answer to each stage of your calculations.

(i) The percentage loss in mass on heating is defi ned as

the original massthe loss in mass on heating × 100.

Calculate the percentage loss in mass of FA 4.

percentage loss in mass = ............................. %

(ii) Calculate the percentage loss in mass when pure hydrated calcium chloride, CaCl 2.2H2O, is heated.

percentage loss in mass = ............................. %

(iii) Use your results to (i) and (ii) to calculate the percentage purity of FA 4, impure CaCl 2.2H2O.

percentage purity = ............................. %[3]

(c) A student carried out this experiment using 2.60 g of FA 4.

Suggest whether this experiment would give a more accurate result for the percentage purity of FA 4. Explain your answer.

....................................................................................................................................................

.............................................................................................................................................. [1]

6

9701/33/O/N/15© UCLES 2015

(d) In your calculations you assumed that the impurity in FA 4 does not decompose on heating.

State how the percentage purity that you calculated in (b)(iii) would change if the impurity were to decompose on heating.


....................................................................................................................................................

.............................................................................................................................................. [1]

[Total: 11]

7





Where gases are released they should be identifi ed by a test, described in the appropriate place in your observations.





(a) (i) FA 5, FA 6 and FA 7 are aqueous solutions each containing one anion and one cation.

Carry out the experiments described below and record your observations for each solution in the table.

FA 5 FA 6 FA 7To a 1 cm depth in a test-tube, add a 1 cm depth of aqueous sodium carbonate.To a 1 cm depth in atest-tube, add a 1 cm depth of aqueous copper(II) sulfate.To a 1 cm depth in atest-tube, add a 1 cm depth of aqueousbarium chloride or aqueous barium nitrate.

(ii) What ion is present in both FA 6 and FA 7?

.............................................................................................................................................

(iii) The anion in FA 5 is one of carbonate, chloride, nitrate or sulfate.

Which anion is present in FA 5?

.............................................................................................................................................

(iv) Write the ionic equation, including state symbols, for the reaction between FA 5 and aqueous copper(II) sulfate.

.............................................................................................................................................[7]

8

9701/33/O/N/15© UCLES 2015

(b) FA 8 contains two anions and two cations from the lists on pages 10 and 11.

• To a 5 cm depth of distilled water in a boiling tube, add all the FA 8. • Shake the boiling tube thoroughly for one minute to make sure that no more of the solid

will dissolve. • Filter the mixture into a clean boiling tube. • Place the filter funnel in a conical flask and wash the residue with a little distilled water. • Keep both filtrate and residue for tests (i) and (ii) below.

(i) Tests on the fi ltrate (the solution in the boiling tube)

Carry out the following tests and record your observations in the table below.

test observationsTo a 1 cm depth of the fi ltrate in a test-tube, add aqueous sodium hydroxide, then

add aqueous hydrogen peroxide.

(ii) Tests on the residue

Carry out the following tests and record your observations in the table below.

test observationsPlace the funnel containing the residue into a clean boiling tube. Pour approximately 5 cm3 of dilute nitric acid onto the residue. Collect a 1 cm depth of solution in the boiling tube. Remove the funnel and return it to the conical fl ask.To this solution in the boiling tube, add aqueous sodium hydroxide.

9


(iii) Identify two cations present in FA 8.

cations present .......................... and ..........................

(iv) Identify one anion present in FA 8.

anion present ..........................

(v) Suggest what type of reaction is happening when hydrogen peroxide is added in test (b)(i).

.............................................................................................................................................[8]

[Total: 15]

10

9701/33/O/N/15© UCLES 2015




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4


–

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)



11

9701/33/O/N/15© UCLES 2015


ion reaction

carbonate,CO3

2–


chloride,Cl –(aq)

gives white ppt. with Ag+(aq) (soluble in NH3(aq))

bromide,Br


iodide,I –(aq)

gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq))

nitrate,NO3


nitrite,NO2

–(aq)


sulfate,SO4


sulfi te,SO3


3 Tests for gases







sulfur dioxide, SO2 turns acidifi ed aqueous potassium manganate(VII) from purple to colourless

12

9701/33/O/N/15© UCLES 2015


Gro

up

140

Ce

Cer

ium

58

141

PrP

rase

odym

ium

59

144

Nd

Neo

dym

ium

60

PmP

rom

ethi

um61

150

SmS

amar

ium

62

152

EuE

urop

ium

63

157

Gd

Gad

olin

ium

64

159

Tb Terb

ium

65

163

Dy

Dys

pros

ium

66

165

Ho

Hol

miu

m67

167

Er Erb

ium

68

169

Tm Thul

ium

69

173

YbY

tterb

ium

70

175

LuLu

tetiu

m71

Th Thor

ium

90

PaP

rota

ctin

ium

91

UU

rani

um92

Np

Nep

tuni

um93

PuP

luto

nium

94

Am

Am

eric

ium

95

Cm

Cur

ium

96

Bk

Ber

keliu

m97

Cf

Cal

iforn

ium

98

EsE

inst

eini

um99

Fm Ferm

ium

100

Md

Men

dele

vium

101

No

Nob

eliu

m10

2

LrLa

wre

nciu

m10

3

1.0 H

Hyd

roge

n1

6.9 Li

Lith

ium

3

23.0

Na

Sod

ium

11

24.3

Mg

Mag

nesi

um12

40.1

Ca

Cal

cium

20

45.0 Sc

Sca

ndiu

m21

47.9 Ti

Tita

nium

22

50.9 V

Vana

dium

23

52.0 Cr

Chr

omiu

m24

54.9

Mn

Man

gane

se25

55.8 Fe Iron

26

58.9

Co

Cob

alt

27

58.7 Ni

Nic

kel

28

63.5

Cu

Cop

per

29

65.4

Zn Zinc

30

69.7

Ga

Gal

lium

31

27.0 Al

Alu

min

ium

13

10.8 B B

oron

5

12.0 C

Car

bon

6

14.0 N

Nitr

ogen

7

16.0 O

Oxy

gen

8

19.0 F

Fluo

rine

9

28.1 Si S

ilico

n14

31.0 P

Pho

spho

rus

15

32.1 S S

ulfu

r16

35.5 Cl

Chl

orin

e17

39.9 Ar

Arg

on18

20.2 Ne

Neo

n10

4.0

He

Hel

ium

2

72.6

Ge

Ger

man

ium

32

74.9

As

Ars

enic

33

79.0 Se

Sel

eniu

m34

79.9 Br

Bro

min

e35

83.8 Kr

Kry

pton

36

39.1 K

Pot

assi

um19

87.6 Sr

Stro

ntiu

m38

88.9 Y

Yttr

ium

39

91.2 Zr

Zirc

oniu

m40

92.9

Nb

Nio

bium

41

95.9

Mo

Mol

ybde

num

42

TcTe

chne

tium

43

101

Ru

Rut

heni

um44

103

Rh

Rho

dium

45

106

PdP

alla

dium

46

108

Ag

Silv

er47

112

Cd

Cad

miu

m48

115

In Indi

um49

119

Sn Tin

50

122

SbA

ntim

ony

51

128

TeTe

lluriu

m52

127 I

Iodi

ne53

131

Xe Xen

on54

137

Ba

Bar

ium

56

139

LaLa

ntha

num

57

*

178

Hf

Haf

nium

72

181

TaTa

ntal

um73

184 W

Tung

sten

74

186

Re

Rhe

nium

75

190

Os

Osm

ium

76

192

Ir Iridi

um77

195 Pt

Pla

tinum

78

197

Au

Gol

d79

201

Hg

Mer

cury

80

204 Tl

Thal

lium

81

207

Pb Lead

82

209 Bi

Bis

mut

h83

PoP

olon

ium

84

At

Ast

atin

e85

Rn

Rad

on86

Rf

Rut

herfo

rdiu

m10

4

Db

Dub

nium

105

SgS

eabo

rgiu

m10

6

Bh

Boh

rium

107

Hs

Has

sium

108

Mt

Mei

tner

ium

109

Uun

Unu

nnili

um11

0

Uuu

Unu

nuni

um11

1

Uub

Unu

nbiu

m11

2

Uuq

Unu

nqua

dium

114

Uuh

Unu

nhex

ium

116

Uuo

Unu

noct

ium

118

FrFr

anci

um87

Ac

Act

iniu

m89

9.0

Be

Ber

ylliu

m4

III

IIIIV

VV

IV

II0

85.5

Rb

Rub

idiu

m37

133

Cs

Cae

sium

55

Ra

Rad

ium

88 a Xb

a =

rela

tive

atom

ic m

ass

X =

atom

ic s

ymbo

l

b =

prot

on (a

tom

ic) n

umbe

r

Key

* 58-

71 L

anth

anid

es90

-103

Act

inid

es

The

Perio

dic

Tabl

e of

the

Elem

ents

*




Qualitative Analysis Notes are printed on pages 10 and 11.A Periodic Table is printed on page 12.


CHEMISTRY 9701/34


2 hours






*9629032111*

Session

Laboratory


1

2

3

Total

2

9701/34/O/N/15© UCLES 2015

I

II

III

IV

V

VI

VII

1 In this experiment you will determine the relative atomic mass, Ar, of magnesium by a titration method.

FB 1 is 2.00 mol dm–3 hydrochloric acid, HCl. FB 3 is 0.120 mol dm–3 sodium hydroxide, NaOH. magnesium ribbon bromophenol blue indicator

(a) Method

Reaction of magnesium with FB 1 ● Pipette 25.0 cm3 of FB 1 into the 250 cm3 beaker. ● Weigh the strip of magnesium ribbon and record its mass.

mass of magnesium = ................... g

● Coil the strip of magnesium ribbon loosely and then add it to the FB 1 in the beaker. ● Stir the mixture occasionally and wait until the reaction has finished.

Dilution of the excess acid ● Transfer all the solution from the beaker into the volumetric flask. ● Make the solution up to the mark using distilled water. ● Shake the flask to mix the solution before using it for your titrations. ● Label this solution of hydrochloric acid FB 2.

Titration ● Fill the burette with FB 2. ● Rinse the pipette out thoroughly. Then pipette 25.0 cm3 of FB 3 into a conical fl ask. ● Add several drops of bromophenol blue indicator. ● Perform a rough titration, by running the solution from the burette into the conical fl ask

until the mixture just becomes yellow. ● Record your burette readings in the space below.

The rough titre is ................... cm3.

● Carry out as many accurate titrations as you think necessary to obtain consistent results. ● Make sure any recorded results show the precision of your practical work. ● Record in a suitable form below all of your burette readings and the volume of FB 2 added


[7]

3


(b) From your accurate titration results, obtain a suitable value for the volume of FB 2 to be used in your calculations.


25.0 cm3 of FB 3 required ................... cm3 of FB 2. [1]

(c) Calculations

Show your working and appropriate signifi cant fi gures in the fi nal answer to each step of your calculations.

(i) Calculate the number of moles of sodium hydroxide present in 25.0 cm3 of solution FB 3.

moles of NaOH = ................... mol

(ii) Give the equation for the reaction of hydrochloric acid, HCl, with sodium hydroxide, NaOH. State symbols are not required.

.............................................................................................................................................

Deduce the number of moles of hydrochloric acid in the volume of FB 2 you calculated in (b).

moles of HCl = ................... mol

(iii) Calculate the number of moles of hydrochloric acid in 250 cm3 of FB 2.

moles of HCl in 250 cm3 of FB 2 = ................... mol

(iv) Calculate the number of moles of hydrochloric acid in 25.0 cm3 of FB 1.

moles of HCl in 25.0 cm3 of FB 1 = ................... mol

4

9701/34/O/N/15© UCLES 2015

(v) In (a), you reacted 25.0 cm3 of FB 1 with your weighed piece of magnesium. After the reaction, the unreacted hydrochloric acid was used to prepare 250 cm3 of FB 2.

Use your answers to (iii) and (iv) to calculate the number of moles of hydrochloric acid that reacted with the magnesium ribbon.

moles of HCl reacting with Mg = ................... mol

(vi) Complete the equation below, for the reaction of magnesium with hydrochloric acid. State symbols are required.

Mg + HCl → MgCl 2 + ............................

Use your answer to (v) to calculate the number of moles of magnesium used.

moles of Mg = ................... mol

(vii) Use your answer to (vi) to calculate the relative atomic mass, Ar, of magnesium.

Ar of Mg = ...................[6]

(d) (i) State one observation that proves that the hydrochloric acid in FB 1 was in excess for the reaction with the magnesium ribbon.

.............................................................................................................................................

.............................................................................................................................................

(ii) A student carried out exactly the same experiment but used 1.00 g of magnesium ribbon. State and explain why the student’s experiment could not be used to determine the value

for the Ar of magnesium. Include a calculation in your answer.

.............................................................................................................................................

.............................................................................................................................................[3]

[Total: 17]

5


2 In this experiment you will determine the relative atomic mass of magnesium by thermal decomposition of hydrated magnesium sulfate.

MgSO4.7H2O(s) → MgSO4(s) + 7H2O(g)

FB 4 is hydrated magnesium sulfate, MgSO4.7H2O.

(a) Method

Record all your weighings in the space below.

● Weigh the crucible with its lid. ● Transfer all FB 4 into the crucible. ● Weigh the crucible, lid and FB 4. ● Place the crucible on the pipe-clay triangle. ● Heat the crucible gently with the lid on, for about one minute. ● Then heat the crucible strongly, without the lid, for a further four minutes. ● Leave the crucible and its contents to cool with the lid on, for several minutes. ● While the crucible is cooling, begin work on Question 3. ● When the crucible has cooled, weigh it, with the lid and contents. ● Calculate and record the mass of anhydrous magnesium sulfate produced and the mass

of water lost.

[3]

(b) Calculations

(i) Calculate the number of moles of water lost during heating. (Use the data in the Periodic Table on page 12.)

moles of H2O = ................... mol

(ii) Use the equation above and your answer to (i) to calculate the number of moles of anhydrous magnesium sulfate produced.

moles of MgSO4 = ................... mol

I

II

III

6

9701/34/O/N/15© UCLES 2015

(iii) Use your weighings and your answer to (ii) to calculate the relative formula mass, Mr, of anhydrous magnesium sulfate.

Mr of MgSO4 = ...................

(iv) From your answer to (iii), calculate the relative atomic mass, Ar, of magnesium.

Ar of Mg = ...................[4]

(c) (i) How could the experiment be improved to ensure that the magnesium sulfate had been completely dehydrated?

.............................................................................................................................................

.............................................................................................................................................

(ii) Why is the lid put on the crucible during cooling?

.............................................................................................................................................

.............................................................................................................................................[2]

[Total: 9]

7






You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted.




(a) FB 5 is a solution containing one cation and one anion. Carry out test-tube tests to fi nd out whether the cation in FB 5 is magnesium and whether the

anion is sulfate.

● State what reagents you used. ● Record the observations you made in a table. ● State your conclusions about which ions are present.

[4]

8

9701/34/O/N/15© UCLES 2015

(b) FB 6 is a salt containing one cation and one anion from those listed on pages 10 and 11.

(i) Place a few crystals of FB 6 in a hard-glass test-tube. Heat gently at fi rst and then strongly. Leave the test-tube and its contents to cool.

Record all your observations below.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(ii) Dissolve the remainder of FB 6 in about 20 cm3 of distilled water in a boiling tube for use in the following tests.

test observationsTo a 1 cm depth of the solution of FB 6 in a test-tube, add a few drops of aqueous silver nitrate.

To a 1 cm depth of the solution of FB 6 in a test-tube, add a few drops of dilute sulfuric acid.

To a 1 cm depth of the solution of FB 6 in a test-tube, add aqueous ammonia.

9


test observationsTo a 1 cm depth of the solution of FB 6 in a boiling tube, add aqueous sodium hydroxide until in excess, then

heat the mixture gently and carefully, and test any gas produced, then

add a small piece of aluminium foil while the mixture is still warm. Test any gas produced.

(iii) Deduce the formula of the salt in FB 6.

Formula is ........................................[10]

[Total: 14]

10

9701/34/O/N/15© UCLES 2015




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4


–

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)



11

9701/34/O/N/15© UCLES 2015


ion reaction

carbonate,CO3

2–


chloride,Cl –(aq)


bromide,Br


iodide,I –(aq)


nitrate,NO3


nitrite,NO2

–(aq)


sulfate,SO4


sulfi te,SO3


3 Tests for gases







sulfur dioxide, SO2turns acidifi ed aqueous potassium manganate(VII) from purple to colourless

12

9701/34/O/N/15© UCLES 2015


Gro

up

140

Ce

Cer

ium

58

141

PrP

rase

odym

ium

59

144

Nd

Neo

dym

ium

60

PmP

rom

ethi

um61

150

SmS

amar

ium

62

152

EuE

urop

ium

63

157

Gd

Gad

olin

ium

64

159

Tb Terb

ium

65

163

Dy

Dys

pros

ium

66

165

Ho

Hol

miu

m67

167

Er Erb

ium

68

169

Tm Thul

ium

69

173

YbY

tterb

ium

70

175

LuLu

tetiu

m71

Th Thor

ium

90

PaP

rota

ctin

ium

91

UU

rani

um92

Np

Nep

tuni

um93

PuP

luto

nium

94

Am

Am

eric

ium

95

Cm

Cur

ium

96

Bk

Ber

keliu

m97

Cf

Cal

iforn

ium

98

EsE

inst

eini

um99

Fm Ferm

ium

100

Md

Men

dele

vium

101

No

Nob

eliu

m10

2

LrLa

wre

nciu

m10

3

1.0 H

Hyd

roge

n1

6.9 Li

Lith

ium

3

23.0

Na

Sod

ium

11

24.3

Mg

Mag

nesi

um12

40.1

Ca

Cal

cium

20

45.0 Sc

Sca

ndiu

m21

47.9 Ti

Tita

nium

22

50.9 V

Vana

dium

23

52.0 Cr

Chr

omiu

m24

54.9

Mn

Man

gane

se25

55.8 Fe Iron

26

58.9

Co

Cob

alt

27

58.7 Ni

Nic

kel

28

63.5

Cu

Cop

per

29

65.4

Zn Zinc

30

69.7

Ga

Gal

lium

31

27.0 Al

Alu

min

ium

13

10.8 B B

oron

5

12.0 C

Car

bon

6

14.0 N

Nitr

ogen

7

16.0 O

Oxy

gen

8

19.0 F

Fluo

rine

9

28.1 Si S

ilico

n14

31.0 P

Pho

spho

rus

15

32.1 S S

ulfu

r16

35.5 Cl

Chl

orin

e17

39.9 Ar

Arg

on18

20.2 Ne

Neo

n10

4.0

He

Hel

ium

2

72.6

Ge

Ger

man

ium

32

74.9

As

Ars

enic

33

79.0 Se

Sel

eniu

m34

79.9 Br

Bro

min

e35

83.8 Kr

Kry

pton

36

39.1 K

Pot

assi

um19

87.6 Sr

Stro

ntiu

m38

88.9 Y

Yttr

ium

39

91.2 Zr

Zirc

oniu

m40

92.9

Nb

Nio

bium

41

95.9

Mo

Mol

ybde

num

42

TcTe

chne

tium

43

101

Ru

Rut

heni

um44

103

Rh

Rho

dium

45

106

PdP

alla

dium

46

108

Ag

Silv

er47

112

Cd

Cad

miu

m48

115

In Indi

um49

119

Sn Tin

50

122

SbA

ntim

ony

51

128

TeTe

lluriu

m52

127 I

Iodi

ne53

131

Xe Xen

on54

137

Ba

Bar

ium

56

139

LaLa

ntha

num

57

*

178

Hf

Haf

nium

72

181

TaTa

ntal

um73

184 W

Tung

sten

74

186

Re

Rhe

nium

75

190

Os

Osm

ium

76

192

Ir Iridi

um77

195 Pt

Pla

tinum

78

197

Au

Gol

d79

201

Hg

Mer

cury

80

204 Tl

Thal

lium

81

207

Pb Lead

82

209 Bi

Bis

mut

h83

PoP

olon

ium

84

At

Ast

atin

e85

Rn

Rad

on86

Rf

Rut

herfo

rdiu

m10

4

Db

Dub

nium

105

SgS

eabo

rgiu

m10

6

Bh

Boh

rium

107

Hs

Has

sium

108

Mt

Mei

tner

ium

109

Uun

Unu

nnili

um11

0

Uuu

Unu

nuni

um11

1

Uub

Unu

nbiu

m11

2

Uuq

Unu

nqua

dium

114

Uuh

Unu

nhex

ium

116

Uuo

Unu

noct

ium

118

FrFr

anci

um87

Ac

Act

iniu

m89

9.0

Be

Ber

ylliu

m4

III

IIIIV

VV

IV

II0

85.5

Rb

Rub

idiu

m37

133

Cs

Cae

sium

55

Ra

Rad

ium

88 a Xb

a =

rela

tive

atom

ic m

ass

X =

atom

ic s

ymbo

l

b =

prot

on (a

tom

ic) n

umbe

r

Key

* 58-

71 L

anth

anid

es90

-103

Act

inid

es

The

Perio

dic

Tabl

e of

the

Elem

ents

*



Answer all questions.Electronic calculators may be used.You may lose marks if you do not show your working or if you do not use appropriate units.Use of a Data Booklet is unnecessary.A copy of the Periodic Table is printed on page 12.



CHEMISTRY 9701/35


2 hours




This document consists of 12 printed pages and 1 insert.


*6080416943*

Session

Laboratory


1

2

3

Total

2

9701/35/O/N/15© UCLES 2015

1 In this experiment you will determine the ionic equation for the reaction of acidifi ed potassium manganate(VII) with potassium iodide. Excess potassium iodide is used and the reaction produces iodine. The amount of iodine produced is measured by titration with sodium thiosulfate.

FA 1 is 0.0180 mol dm–3 potassium manganate(VII), KMnO4. FA 2 is 1.00 mol dm–3 sulfuric acid, H2SO4. FA 3 is 0.500 mol dm–3 potassium iodide, KI. FA 4 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. starch indicator

(a) Method

● Pipette 25.0 cm3 of FA 1 into a conical fl ask. ● Use the measuring cylinder to add 25 cm3 of FA 2 to the conical fl ask. ● Use the measuring cylinder to add 20 cm3 of FA 3 to the conical fl ask. ● Fill the burette with FA 4. ● Carry out a rough titration. When the colour of the mixture becomes yellow/orange, add a

few drops of starch indicator. Then titrate until the mixture goes colourless. ● Record all your burette readings in the space below.

The rough titre is ........................ cm3.

● Carry out as many accurate titrations as you think necessary to obtain consistent results. ● Make sure any recorded results show the precision of your practical work. ● Record in a suitable form below all of your burette readings and the volume of FA 4 added


Keep FA 1 and FA 2 for use in Question 3 and FA 4 for use in Question 2.

[7]

(b) From your accurate titration results, obtain a suitable value for the volume of FA 4 to be used in your calculations.


Volume of FA 4 required is ..................... cm3. [1]

I

II

III

IV

V

VI

VII

3


(c) Calculations


(i) Calculate the number of moles of sodium thiosulfate in the volume of FA 4 calculatedin (b).

moles of Na2S2O3 = ............................. mol

(ii) Use the equation below to calculate the number of moles of iodine that reacted with the sodium thiosulfate in the titration.

I2 + 2Na2S2O3 → Na2S4O6 + 2NaI

moles of I2 = ............................. mol

(iii) Use information on page 2 to calculate the number of moles of potassium manganate(VII) in FA 1 used in the titration.

moles of KMnO4 = ............................. mol

(iv) From your answers to (ii) and (iii), calculate the number of moles of iodine produced by the reaction of 2.00 moles of potassium manganate(VII) with excess potassium iodide.

moles I2 = ............................. mol

(v) Using your answer to (iv), put a tick next to the ionic equation that represents the reaction between FA 1 and FA 3.

2MnO4– + 2I– + 16H+ → I2 + 2Mn6+ + 8H2O ...........

2MnO4– + 4I– + 16H+ → 2I2 + 2Mn5+ + 8H2O ...........

2MnO4– + 6I– + 16H+ → 3I2 + 2Mn4+ + 8H2O ...........

2MnO4– + 8I– + 16H+ → 4I2 + 2Mn3+ + 8H2O ...........

2MnO4– + 10I– + 16H+ → 5I2 + 2Mn2+ + 8H2O ...........

2MnO4– + 12I– + 16H+ → 6I2 + 2Mn+ + 8H2O ...........

4

9701/35/O/N/15© UCLES 2015

(vi) Prove that the iodide ion has been oxidised in the equation that you selected in (v).

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[5]

(d) (i) The error in calibration of the pipette you used is ±0.06 cm3. Calculate the percentage error when measuring FA 1, using the pipette.

percentage error = ..................... %

(ii) A student suggested that the experiment would be more accurate if a pipette was used to measure solution FA 3.

State and explain whether you agree with the student.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

[Total: 15]

5


2 In this experiment you will investigate how the rate of reaction between sodium thiosulfate and hydrochloric acid is affected by the concentration of the acid.

When aqueous thiosulfate ions react with hydrogen ions, H+, in any acid, a pale yellow precipitate of sulfur is formed. The ionic equation for this reaction is given below.

S2O32–(aq) + 2H+(aq) → S(s) + SO2(aq) + H2O(l)

The rate of the reaction can be determined by measuring the time taken to produce a fi xed quantity of sulfur.

FA 4 is 0.10 mol dm–3 sodium thiosulfate, Na2S2O3. FA 5 is 0.20 mol dm–3 hydrochloric acid, HCl.

(a) Method

Record all your measurements, in an appropriate form, in the space below.

Experiment 1

● Use the larger measuring cylinder to transfer 40 cm3 of FA 4 into the 100 cm3 beaker. ● Rinse the larger measuring cylinder thoroughly with water, then add 30 cm3 of FA 5 to the

beaker and start timing immediately. ● Stir the mixture once and place the beaker on top of the printed insert page provided. ● Look down through the solution in the beaker at the print on the insert. ● Stop timing as soon as the precipitate of sulfur makes the print on the insert invisible. ● Record the reaction time to the nearest second. ● Empty and rinse the 100 cm3 beaker. ● Dry the outside of the beaker ready for Experiment 2.

Experiment 2

● Rinse the larger measuring cylinder, then use it to transfer 40 cm3 of FA 4 into the 100 cm3 beaker.

● Use the smaller measuring cylinder to add 10 cm3 of distilled water to the beaker. ● Use the same measuring cylinder to add 20 cm3 of FA 5 to the mixture in the beaker and

start timing immediately. ● Stir the mixture once and place the beaker on top of the printed insert page provided. ● Stop timing as soon as the print on the insert becomes invisible. ● Record the reaction time to the nearest second. ● Empty and rinse the 100 cm3 beaker. ● Dry the outside of the beaker ready for Experiment 3.

Experiment 3

● Carry out the reaction using a mixture of 40 cm3 of FA 4, 20 cm3 of distilled water and 10 cm3 of FA 5.

● Measure and record the reaction time to the nearest second.

[4]

I

II

III

IV

6

9701/35/O/N/15© UCLES 2015

(b) (i) The ‘rate of reaction’ can be represented by the formula below.

‘rate of reaction’ = reaction time1000

Use this formula to calculate the ‘rate of reaction’ for Experiments 1 and 3. Give the unit.



(ii) Calculate the initial concentrations of hydrochloric acid in the reaction mixtures in Experiments 1 and 3.



(iii) How is the ‘rate of reaction’ affected by the concentration of hydrochloric acid in the mixture?

.............................................................................................................................................

.............................................................................................................................................

(iv) Predict how the reaction time measured in Experiment 1 would have been affected if the experiment had been carried out using 0.20 mol dm–3 sulfuric acid instead of 0.20 mol dm–3 hydrochloric acid.


.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(v) Predict how the reaction time measured in Experiment 3 would have been affected if the experiment had been carried out in a 250 cm3 beaker instead of a 100 cm3 beaker.


.............................................................................................................................................

.............................................................................................................................................[5]

[Total: 9]

7










(a) FA 6 is a sodium compound containing one anion listed on page 11.

Dissolve the FA 6 provided in about 15 cm3 of distilled water in a boiling tube. Carry out the following tests and record your observations in the table below.

test observations (i) To a 1cm depth of the solution

of FA 6 in a test-tube, add a few drops of aqueous barium chloride or aqueous barium nitrate, then


(ii) To a 1cm depth of the solution of FA 6 in a test-tube, add an equal volume of aqueous hydrogen peroxide, then

add a few drops of aqueous barium chloride or aqueous barium nitrate, then


8

9701/35/O/N/15© UCLES 2015

test observations (iii) To a 1 cm depth of the solution

of FA 6 in a boiling tube, add an equal volume of FA 2, sulfuric acid, then

heat the mixture gently and cautiously.

(iv) To a 1 cm depth of the solution of FA 6 in a test-tube, add an equal volume of aqueous sodium hydroxide, then

add a few drops of FA 1, aqueous potassium manganate(VII), then

add FA 2, sulfuric acid.

(v) Identify the anion in FA 6, and state one piece of evidence for your identifi cation.

anion ...............................................

evidence .............................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

(vi) Give the chemical equation for the reaction between FA 6 and hydrogen peroxide, H2O2, in test (ii). State symbols are not required.

.............................................................................................................................................[7]

9


(b) FA 7, FA 8, FA 9 and FA 10 each contain one cation from the list on page 10. You will attempt to identify the cations by testing with aqueous sodium hydroxide and aqueous

ammonia. In each case, use a 1 cm depth of the solution in a test-tube.

(i) Complete the table below.

testobservations

FA 7 FA 8 FA 9 FA 10

add sodiumhydroxide

add aqueousammonia

(ii) Use your observations to identify, as far as possible, the cation present in each solution. If alternative identities are possible, state this clearly.

FA 7 cation ....................................................

FA 8 cation ....................................................

FA 9 cation ....................................................

FA 10 cation ..................................................

(iii) Give the ionic equation for the reaction of one of your cations with a few drops of sodium hydroxide. State symbols are not required.

.............................................................................................................................................

(iv) The precipitates obtained when alkalis are added to solutions of certain cations are sometimes diffi cult to see. Suggest how, using no additional apparatus, the experiment could be repeated in a way that would make these precipitates more visible.

.............................................................................................................................................

.............................................................................................................................................[9]

[Total: 16]

10

9701/35/O/N/15© UCLES 2015




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4


–

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)



11

9701/35/O/N/15© UCLES 2015


ion reaction

carbonate,CO3

2–


chloride,Cl –(aq)


bromide,Br


iodide,I –(aq)


nitrate,NO3


nitrite,NO2

–(aq)


sulfate,SO4


sulfi te,SO3


3 Tests for gases








12

9701/35/O/N/15© UCLES 2015


Gro

up

140

Ce

Cer

ium

58

141

PrP

rase

odym

ium

59

144

Nd

Neo

dym

ium

60

PmP

rom

ethi

um61

150

SmS

amar

ium

62

152

EuE

urop

ium

63

157

Gd

Gad

olin

ium

64

159

Tb Terb

ium

65

163

Dy

Dys

pros

ium

66

165

Ho

Hol

miu

m67

167

Er Erb

ium

68

169

Tm Thul

ium

69

173

YbY

tterb

ium

70

175

LuLu

tetiu

m71

Th Thor

ium

90

PaP

rota

ctin

ium

91

UU

rani

um92

Np

Nep

tuni

um93

PuP

luto

nium

94

Am

Am

eric

ium

95

Cm

Cur

ium

96

Bk

Ber

keliu

m97

Cf

Cal

iforn

ium

98

EsE

inst

eini

um99

Fm Ferm

ium

100

Md

Men

dele

vium

101

No

Nob

eliu

m10

2

LrLa

wre

nciu

m10

3

1.0 H

Hyd

roge

n1

6.9 Li

Lith

ium

3

23.0

Na

Sod

ium

11

24.3

Mg

Mag

nesi

um12

40.1

Ca

Cal

cium

20

45.0 Sc

Sca

ndiu

m21

47.9 Ti

Tita

nium

22

50.9 V

Vana

dium

23

52.0 Cr

Chr

omiu

m24

54.9

Mn

Man

gane

se25

55.8 Fe Iron

26

58.9

Co

Cob

alt

27

58.7 Ni

Nic

kel

28

63.5

Cu

Cop

per

29

65.4

Zn Zinc

30

69.7

Ga

Gal

lium

31

27.0 Al

Alu

min

ium

13

10.8 B B

oron

5

12.0 C

Car

bon

6

14.0 N

Nitr

ogen

7

16.0 O

Oxy

gen

8

19.0 F

Fluo

rine

9

28.1 Si S

ilico

n14

31.0 P

Pho

spho

rus

15

32.1 S S

ulfu

r16

35.5 Cl

Chl

orin

e17

39.9 Ar

Arg

on18

20.2 Ne

Neo

n10

4.0

He

Hel

ium

2

72.6

Ge

Ger

man

ium

32

74.9

As

Ars

enic

33

79.0 Se

Sel

eniu

m34

79.9 Br

Bro

min

e35

83.8 Kr

Kry

pton

36

39.1 K

Pot

assi

um19

87.6 Sr

Stro

ntiu

m38

88.9 Y

Yttr

ium

39

91.2 Zr

Zirc

oniu

m40

92.9

Nb

Nio

bium

41

95.9

Mo

Mol

ybde

num

42

TcTe

chne

tium

43

101

Ru

Rut

heni

um44

103

Rh

Rho

dium

45

106

PdP

alla

dium

46

108

Ag

Silv

er47

112

Cd

Cad

miu

m48

115

In Indi

um49

119

Sn Tin

50

122

SbA

ntim

ony

51

128

TeTe

lluriu

m52

127 I

Iodi

ne53

131

Xe Xen

on54

137

Ba

Bar

ium

56

139

LaLa

ntha

num

57

*

178

Hf

Haf

nium

72

181

TaTa

ntal

um73

184 W

Tung

sten

74

186

Re

Rhe

nium

75

190

Os

Osm

ium

76

192

Ir Iridi

um77

195 Pt

Pla

tinum

78

197

Au

Gol

d79

201

Hg

Mer

cury

80

204 Tl

Thal

lium

81

207

Pb Lead

82

209 Bi

Bis

mut

h83

PoP

olon

ium

84

At

Ast

atin

e85

Rn

Rad

on86

Rf

Rut

herfo

rdiu

m10

4

Db

Dub

nium

105

SgS

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*






CHEMISTRY 9701/36


2 hours






*0597751623*

Session

Laboratory


1

2

Total

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9701/36/O/N/15© UCLES 2015

1 You will investigate the rate of reaction between iron(III) ions, Fe3+, and iodide ions, I–.

2Fe3+(aq) + 2I–(aq) → 2Fe2+(aq) + I2(aq)

The iodine, I2, produced can be reacted immediately with thiosulfate ions, S2O32–.

I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O6

2–(aq)

When all the thiosulfate has been used, the iodine produced will turn starch indicator blue-black. The rate of the reaction can therefore be measured by fi nding the time for the blue-black colour to appear.

FB 1 is aqueous iron(III) chloride, FeCl 3. FB 2 is aqueous potassium iodide, KI. FB 3 is 0.0060 mol dm–3 sodium thiosulfate, Na2S2O3. starch indicator

You are advised to read the instructions before starting any practical work and draw a table for your results in the space on page 3.

(a) Method

Experiment 1

● Fill a burette with FB 1. ● Run 20.00 cm3 of FB 1 into a 100 cm3 beaker. ● Use the measuring cylinder to place the following in a second 100 cm3 beaker. ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of starch indicator ● Add the contents of the second beaker to the first beaker and start timing. ● Stir the mixture once and place the beaker on the white tile. ● The mixture turns brown and then yellow before turning a blue-black colour. Stop timing

when this blue-black colour appears. ● Record in your table the volume of FB 1 used, the volume of distilled water used and the

time to the nearest second for the blue-black colour to appear. ● Wash both beakers.

For each of Experiments 2-6 you should complete your results table to show the volume of FB 1 used, the volume of distilled water used and the time taken to the nearest second for the blue-black colour to appear.

Experiment 2

● Fill the other burette with distilled water. ● Run 10.00 cm3 of FB 1 into a 100 cm3 beaker. ● Run 10.00 cm3 of distilled water into the same beaker. ● Use the measuring cylinder to place the following in a second 100 cm3 beaker. ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of starch indicator ● Add the contents of the second beaker to the first beaker and start timing. ● Stir the mixture once and place the beaker on the white tile. ● Stop timing when a blue-black colour appears. ● Wash both beakers.

3


I

II

III

IV

V

VI

VII

VIII

Experiments 3-6

Carry out four further experiments to investigate the effect of changing the concentration of Fe3+(aq) by altering the volume of aqueous FeCl 3, FB 1, used.

You should not use a volume of FB 1 that is less than 6.00 cm3 and the total volume of the reaction mixture must always be 60 cm3.

[8]

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(b) Calculations

The rate of reaction can be found by calculating the change in concentration of Fe3+(aq) that occurred when enough iodine was produced to change the colour of the indicator to blue-black.

Use your data and the equations on page 2 to carry out the following calculations.


(i) Calculate the number of moles of thiosulfate ions, S2O32– used in each experiment in (a).

moles S2O32– = ...................... mol

(ii) Calculate the number of moles of iodine, I2, that react with the number of moles of S2O32–

in (i).

moles I2 = ...................... mol

(iii) Calculate the number of moles of iron(III) ions, Fe3+, that were used to produce the number of moles of iodine in (ii).

moles Fe3+ = ...................... mol

(iv) When the moles of Fe3+ that you calculated in (iii) reacted, a change in the concentration of moles of Fe3+ occurred. Calculate this change in concentration.

change in concentration of Fe3+(aq) = ...................... mol dm–3

(v) The following formula can be used as a measure of the ‘rate of reaction’.

‘rate of reaction’ =change in concentration of Fe3+(aq)

reaction time × 106

Complete the table to show the volume of FB 1, the reaction time and the rate in Experiments 1-6. You should include units.

If you were unable to calculate a value for the change in concentration of Fe3+(aq) in (iv), you should assume it is 2.50 × 10–3 mol dm–3. (Note: this is not the correct value.)

Experiment

1

2

3

4

5

6[5]

5


(c) On the grid, plot the rate (y-axis) against the volume of FB 1 (x-axis). Draw a line of best fi t through the points. You should identify any points you consider anomalous.

[4]

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(d) Using your graph, what conclusion can you reach about the effect of changing the concentration of FeCl 3 on the rate of the reaction between Fe3+(aq) and I–(aq)?

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(e) A student wanted to investigate how changing the concentration of I– would affect the rate of reaction. Explain how this investigation could be carried out.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(f) It was found, by carrying out experiments similar to those used in (a), that increasing the concentration of I– increased the rate of the reaction.

The student suggested modifi cations to the method as used in (a). In each case, state what the effect would be on the reaction time in Experiment 1 and explain how these changes would affect the possible errors in the measurements.

Suggested modifi cation 1 The reaction was carried out using the same volumes of all reagents but with the concentrations

of FB 1 and FB 2 being double their original values.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

Suggested modifi cation 2 The reaction was carried out using half the volume of all reagents.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................[4]

7


(g) (i) Which of the experiments you carried out in (a) had the greatest percentage error in the reaction time?

.............................................................................................................................................

(ii) Calculate this percentage error. Assume that the error in measuring the reaction time is ±0.5 s.

percentage error = ................. %[2]

[Total: 27]

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You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted.




Half fi ll the 250 cm3 beaker with water and heat it to about 80 °C and then switch off the burner. This will be used as a water bath in (b).

Keep two clean, dry test-tubes for use in (b).

(a) FB 4 and FB 5 each contain two cations and one anion. One of the cations in FB 4 is the same as one of the cations in FB 5. The anion in FB 4 is the same as the anion in FB 5.

(i) Separately dissolve about half of each of your samples of FB 4 and FB 5 in about 5 cm depth of distilled water in a boiling tube.

Carry out the following tests and record your observations in the table.

testobservations

FB 4 FB 5To a 1 cm depth of solution in a test-tube, add a 1 cm depth of aqueous edta.

To a 1 cm depth of solution in a test-tube, add a 1 cm depth of aqueous potassium iodide.

9


testobservations

FB 4 FB 5To a 1 cm depth of solution in a test-tube, add aqueous sodium hydroxide.

To a 1 cm depth of solution in a test-tube, add aqueous ammonia.

To a 1 cm depth of solution in a test-tube, add a 1 cm depth of aqueous barium chloride or aqueous barium nitrate, then


(ii) From the observations identify three of the ions present in FB 4 and FB 5.

The anion present in both FB 4 and FB 5 is ....................................... .

One cation present in FB 4 is ....................................... .

One cation present in FB 5 is ....................................... .

(iii) FB 4 and FB 5 each contain another cation from the list on page 11. This cation is the same in both FB 4 and FB 5.

Carry out a test to identify this cation. Record details of the test and your observations.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

Identify the cation present in both FB 4 and FB 5.

Cation is .................................... .[8]

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9701/36/O/N/15© UCLES 2015

(b) FB 6 is an aqueous solution of an organic compound.

(i) Complete the table below. The observation with 2,4-dinitrophenylhydrazine has already been made.

test observationsTo a 1 cm depth of FB 6 in a test-tube, a few drops of 2,4-dinitrophenylhydrazine were added.

orange precipitate formed

To a 1 cm depth of FB 6 in a test-tube, add a 2 cm depth of dilute sulfuric acid. Place the test-tube in the water bath. Then add two or three drops of acidifi ed aqueous potassium manganate(VII).

To a 1 cm depth of aqueous silver nitrate in a test-tube, add a few drops of aqueous sodium hydroxide. Then add aqueous ammonia until the brown precipitate just dissolves. To this, add a 1 cm depth of FB 6. Place the test-tube in the water bath and leave to stand.Care: rinse the tube as soon as you have completed this test.

(ii) What conclusion can you make about the identity of FB 6 from the observation of its reaction with 2,4-dinitrophenylhydrazine?

.............................................................................................................................................

(iii) What conclusion can you make about the identity of FB 6 from the observation of its reactions with acidifi ed potassium manganate(VII) and silver nitrate in ammonia solution?

.............................................................................................................................................

(iv) What change in the oxidation state of silver occurs in the reaction between FB 6 and silver nitrate in ammonia solution?

change from .............................. to ..............................[5]

[Total: 13]

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ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4


–

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)



12

9701/36/O/N/15© UCLES 2015





ion reaction

carbonate,CO3

2–


chloride,Cl –(aq)


bromide,Br


iodide,I –(aq)


nitrate,NO3


nitrite,NO2

–(aq)


sulfate,SO4


sulfi te,SO3


3 Tests for gases









Write your Centre number, candidate number and name on all the work you hand in.Write in dark blue or black pen.You may use an HB pencil for any diagrams or graphs.Do not use staples, paper clips, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.

Section AAnswer all questions.

Section BAnswer all questions.

Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units.A Data Booklet is provided.


CHEMISTRY 9701/41

Paper 4 Structured Questions October/November 2015

2 hours



Cambridge International ExaminationsCambridge International Advanced Level



*4682690078*


1

2

3

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5

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7

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Section A


1 (a) Calcium has atomic number 20.

Complete the electronic structures for a

calcium atom, 1s22s22p6.................................

calcium ion in the +2 oxidation state. 1s22s22p6.................................[1]

(b) Calcium nitrate, Ca(NO3)2, is used in fertilisers and can be prepared by an acid-base reaction.

Write an equation for the preparation of calcium nitrate by an acid-base reaction.

.............................................................................................................................................. [1]

(c) (i) When anhydrous calcium nitrate is heated strongly, it decomposes to leave a white solid.

Identify this white solid and suggest another observation for this reaction.

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) The ease of thermal decomposition of the Group II nitrates decreases down the group.

Explain this trend.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

3


(d) (i) What is meant by the term standard enthalpy change of hydration, ?

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Use the following data to calculate the lattice energy, , of calcium nitrate, Ca(NO3)2(s). You may find it helpful to construct an energy cycle.

enthalpy change value

(Ca2+(g)) –1650 kJ mol–1

(NO3–(g)) –314 kJ mol–1

enthalpy change of solution for Ca(NO3)2(s) –19 kJ mol–1

Ca(NO3)2(s) = ........................... kJ mol–1 [3]

(e) The standard enthalpy change of hydration for Ba2+, (Ba2+(g)), is –1305 kJ mol–1.

Suggest an explanation for why the of the Ba2+ ion is less exothermic than the of the Ca2+ ion.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 12]

4

9701/41/O/N/15© UCLES 2015

2 (a) Complete the table to show the number of unpaired electrons in the outer shell of each of the gaseous atoms, Na to Ar.

Na Mg Al Si P S Cl Ar

number of unpaired electrons

[3]

(b) (i) Complete the table for the reactions of two Period 3 chlorides with water.

Period 3 chloride observations pH of solution formed

SiCl 4

PCl 5

[3]

(ii) Write an equation for the reaction between SiCl 4 and H2O.

....................................................................................................................................... [1]

[Total: 7]

5


3 The transition element iron is the most abundant element in the Earth’s core.

(a) What is meant by the term transition element?

....................................................................................................................................................

.............................................................................................................................................. [1]

(b) In aqueous solution, iron can form complex ions which contain ligands.

(i) Name the type of bonding that occurs between a ligand and a transition element.

....................................................................................................................................... [1]

(ii) Which of the following species can act as a ligand? Complete the table by placing a tick () in the appropriate column to indicate whether the

species can act as a ligand or not.

species can actas a ligand

cannot actas a ligand

NO3–

BF3

H2NCH2CH2NH2

NH4+

[2]

(c) Manganese ions, Mn2+(aq), show some similar chemical properties to those of copper(II) ions, Cu2+(aq).

Use this information and the Data Booklet to suggest the formula of the manganese species formed in each of the following reactions. State the type of reaction taking place in each case.

formula of manganesespecies formed

type ofreaction

Mn2+(aq) + NaOH(aq)

Mn2+(aq) + concentrated HCl

Mn2+(aq) + H2O2(aq)

[5]

[Total: 9]

6

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4 In aqueous solution, 2-chloro-2-methylpropane, (CH3)3CCl, reacts with sodium hydroxide, NaOH. This is a nucleophilic substitution reaction.

(CH3)3CCl (aq) + NaOH(aq) → (CH3)3COH(aq) + NaCl (aq)

(a) Show the mechanism for this reaction. Include all necessary curly arrows, lone pairs and relevant dipoles.

[3]

The rate of this reaction was investigated using a large excess of sodium hydroxide.

(b) The graph below shows the results of the experiment.

0.60

0.50

0.40

0.30

0.20

0.10

00 20 40 60 80 100 120 140 160

time / s

[(CH3)3CCl ]/ mol dm–3

7


The reaction is first order with respect to [(CH3)3CCl ]. This can be confirmed from the graph using half-lives.

(i) What is meant by the half-life of a reaction?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Calculate the half-life for this reaction. Show all your working and show clearly any construction lines on the graph.

[1]

(iii) What would be the effect on the half-life of this reaction if the initial concentration of [(CH3)3CCl ] was doubled?

....................................................................................................................................... [1]

(c) (i) Use the graph in (b) to determine the rate of reaction at 80 s. Show all your working.

rate = ............................. units ............................. [2]

The rate equation for this reaction is shown.

rate = k [(CH3)3CCl ]

(ii) Calculate the value of the rate constant, k, for this reaction and give its units.

k = ............................. units ............................. [1]

[Total: 9]

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9701/41/O/N/15© UCLES 2015

5 X is a metallic element.

(a) (i) Draw a fully labelled diagram to show how the standard electrode potential, E o, of X2+(aq) / X(s) could be measured.

[4]

(ii) What are the conditions needed for the value measured to be a standard electrode potential?

....................................................................................................................................... [1]

(iii) State the charge carriers that transfer current through

the solutions, ............................. the wire. ............................. [1]

9


(b) An electrochemical cell was set up consisting of an X2+(aq) / X(s) half-cell (E o = –0.40 V) and an Ag+(aq) / Ag(s) half-cell (E o = +0.80 V).

(i) Write an equation for the reaction that would take place if the electrodes of this cell were connected by a wire.

....................................................................................................................................... [1]

When the current was allowed to pass for a period of time,

• the Ag electrode gained 1.30 g in mass, • the electrode made of metal X lost 0.67 g in mass.

(ii) Calculate the Ar of metal X; hence suggest an identity for X. Show all your working. Use of the Data Booklet is relevant to this question.

Ar = ...........................

X is ...........................[4]

[Total: 11]

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6 Boron forms many useful compounds.

(a) The compound diborane, B2H6, can be used as a rocket fuel. It can be prepared by the reaction of boron trifluoride, BF3, with sodium borohydride, NaBH4.

Balance this equation.

.......BF3 + .......NaBH4 → .......B2H6 + .......NaBF4[1]

(b) Primary and secondary alcohols can be formed by the reaction of carbonyl compounds with NaBH4, which is a source of hydride ions, H–.

Complete the mechanism for the reaction of butanone with hydride ions, H–, and draw the intermediate in the box. Include all necessary curly arrows and relevant dipoles.

CH2CH3

CH2CH3

O

C

intermediate

OH

Cstep 1 H+

H–

H3CH3C

H

[3]

(c) Borane, BH3, is used to synthesise alcohols from alkenes. The reaction occurs in two steps.

The BH2 group from BH3 bonds to the least substituted carbon atom of the double bond, and the remaining H from BH3 bonds to the other carbon.

CH3 H

CH3 CH3

C C

CH3

CH3

H BH2C C+ BH3

Hstep 1 [O]

CH3

CH3

CH3

H OHC C

H

CH3

(i) Suggest the type of reaction in step 1.

....................................................................................................................................... [1]

11


(ii) The diol Y can be prepared by the same method.

CH3

CH3

H3CCH3

OH

OH

Y

Draw the structure of the diene which could be used to prepare diol Y.

[1]

(d) Benzene, C6H6, and borazine, B3N3H6, have planar, cyclic structures.

(i) Describe the structure of and bonding in benzene, C6H6.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) In borazine, B3N3H6, the boron and nitrogen atoms alternate around the ring. Each ring atom has a single hydrogen atom bonded to it.

All boron-nitrogen bonds in borazine are 0.144 nm in length, whereas in simple compounds B–N and B=N bond lengths are 0.154 nm and 0.136 nm respectively.

Suggest and draw the structure of borazine.

[1]

[Total: 10]

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7 (a) Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route.

In step 3 of this synthesis, a phenol-like compound, S, reacts with intermediate T made from amine R.

Assume that the –SO3– Na+ group does not react.

SO3– Na+

SO3– Na+

O2Nstep 1

step 2

+

Sunset Yellow

step 3 NaOH(aq)

R (C6H6NSO3Na)

TS

Q

OH

Na+ –O3S

NN

(i) Suggest structures for compounds R, S and T and draw them in the boxes above. [3]

(ii) Suggest reagents and conditions for

step 1, .................................................................................................................................

step 2. .................................................................................................................................[3]

(iii) What type of organic salt is formed in step 2?

....................................................................................................................................... [1]

13


(b) Compound W has the following structure.

NH2H2N

O

(i) How many σ and π bonds are present in a molecule of W?

σ bonds ....................... π bonds ....................... [2]

(ii) The products of the reactions of W with cold HCl and with CH3CH2Br are soluble in water but not in organic solvents.

Complete the table for these reactions of W.

reagent structure of product(molecular formula given) type of reaction

HCl

(C4H9N2OCl )

CH3CH2Br

(C6H13N2BrO)

[3]

[Total: 12]

14

9701/41/O/N/15© UCLES 2015

Section B


8 (a) The sequence of bases in DNA is a code for the order of amino acids in the primary structure of proteins.

The diagram represents the stages involved in the formation of a protein from DNA.

DNA

ribosome protein

A

B2

B1

stage 1

etc.

stage 3

stage 2

(i) Identify the biochemical structures, A and B1, B2 etc.

biochemical structure identity

A

B1, B2 etc.[2]

(ii) Name the biochemical processes involved in stages 1 and 3.

process name of biochemical process

stage 1

stage 3[1]

15


(b) Adenine is an integral part of DNA.

N

N

N

NH2

NH

adenine

(i) State the molecular formula of adenine.

....................................................................................................................................... [1]

(ii) Identify the three other nitrogenous bases in DNA.

..................................... ..................................... ..................................... [1]

(iii) DNA has a double helical structure that consists of two strands linked together.

What type of bonding exists between the

phosphate and sugar groups within a DNA strand, ............................................................

different bases on the two strands? ....................................................................................[2]

(c) The breakdown of adenosine triphosphate, ATP, provides the energy for many cellular reactions.

ATP + H2O → ADP + Pi

What type of chemical reaction is this?

.............................................................................................................................................. [1]

(d) X-ray crystallography can be useful in obtaining information about the structures of large organic molecules, such as ATP. The technique involves X-rays interacting with the electrons within the molecule.

(i) Which element in the molecule of ATP will interact most strongly with the X-ray beam?

....................................................................................................................................... [1]

(ii) Explain why X-ray crystallography will not detect hydrogen atoms.

.............................................................................................................................................

....................................................................................................................................... [1]

[Total: 10]

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9 (a) Some metals are essential to biochemical processes.

Complete the following table naming one metal in each case.

biochemical process metal

haemoglobin in oxygen transport

transmission of nerve impulses

enzyme cofactor[2]

(b) Enzymes are a special type of protein molecule that catalyse biochemical reactions.

Explain briefly the mechanism by which an enzyme breaks down a substrate molecule.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

(c) Disulfide bonds play an important role in the stability of some proteins such as the keratin in human hair.

The amino acid involved in the formation of a disulfide bond is cysteine, H2NCH(CH2SH)CO2H.

(i) At which level of protein structure (primary, secondary, tertiary) are disulfide bonds formed?

....................................................................................................................................... [1]

(ii) Use a functional group in cysteine to show how disulfide bonds are formed.

[1]

(iii) What type of chemical reaction is this?

....................................................................................................................................... [1]

17


(d) The NMR spectrum of cysteine, H2NCH(CH2SH)CO2H, shows five absorptions.

After shaking a solution of cysteine with a few drops of D2O, the NMR spectrum shows only two absorptions, E and F, shown below.

E F

(i) Identify the two types of protons responsible for the absorptions E and F.

E .........................................................................................................................................

F ..........................................................................................................................................[1]

(ii) State and explain the splitting patterns of the absorptions E and F.

E .........................................................................................................................................

.............................................................................................................................................

F .........................................................................................................................................

....................................................................................................................................... [2]

[Total: 11]

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10 (a) Aspartame is an artificial sweetener that has the structure shown below.

aspartame

OH

O

O

O NH2

H3C NH

O

(i) Draw a circle around each chiral centre in aspartame. [1]

In the stomach, aspartame is hydrolysed by acid to form three organic products.

(ii) On the diagram above, use arrows to indicate the two bonds that would be hydrolysed in the stomach. [2]

(iii) Draw the structures of the three products formed after complete acid hydrolysis of aspartame.

[3]

19


(b) Aspartame is soluble in water.

By referring to the structure of aspartame, explain why it is soluble in water.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(c) Recently, nanotechnology has been involved in the development of a new natural sweetener, Nano Sugar, extracted from sugar cane.

What is the approximate width of a nanoparticle?

.............................................................................................................................................. [1]

[Total: 9]

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BLANK PAGE










CHEMISTRY 9701/42


2 hours






*2492672497*


1

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Section A


1 (a) Calcium has atomic number 20.

Complete the electronic structures for a

calcium atom, 1s22s22p6.................................

calcium ion in the +2 oxidation state. 1s22s22p6.................................[1]

(b) Calcium nitrate, Ca(NO3)2, is used in fertilisers and can be prepared by an acid-base reaction.

Write an equation for the preparation of calcium nitrate by an acid-base reaction.

.............................................................................................................................................. [1]

(c) (i) When anhydrous calcium nitrate is heated strongly, it decomposes to leave a white solid.

Identify this white solid and suggest another observation for this reaction.

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) The ease of thermal decomposition of the Group II nitrates decreases down the group.

Explain this trend.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

3


(d) (i) What is meant by the term standard enthalpy change of hydration, ?

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) Use the following data to calculate the lattice energy, , of calcium nitrate, Ca(NO3)2(s). You may find it helpful to construct an energy cycle.


(Ca2+(g)) –1650 kJ mol–1

(NO3–(g)) –314 kJ mol–1

enthalpy change of solution for Ca(NO3)2(s) –19 kJ mol–1

Ca(NO3)2(s) = ........................... kJ mol–1 [3]

(e) The standard enthalpy change of hydration for Ba2+, (Ba2+(g)), is –1305 kJ mol–1.

Suggest an explanation for why the of the Ba2+ ion is less exothermic than the of the Ca2+ ion.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 12]

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2 (a) Complete the table to show the number of unpaired electrons in the outer shell of each of the gaseous atoms, Na to Ar.

Na Mg Al Si P S Cl Ar

number of unpaired electrons

[3]

(b) (i) Complete the table for the reactions of two Period 3 chlorides with water.

Period 3 chloride observations pH of solution formed

SiCl 4

PCl 5

[3]

(ii) Write an equation for the reaction between SiCl 4 and H2O.

....................................................................................................................................... [1]

[Total: 7]

5


3 The transition element iron is the most abundant element in the Earth’s core.

(a) What is meant by the term transition element?

....................................................................................................................................................

.............................................................................................................................................. [1]

(b) In aqueous solution, iron can form complex ions which contain ligands.

(i) Name the type of bonding that occurs between a ligand and a transition element.

....................................................................................................................................... [1]

(ii) Which of the following species can act as a ligand? Complete the table by placing a tick () in the appropriate column to indicate whether the

species can act as a ligand or not.

species can actas a ligand

cannot actas a ligand

NO3–

BF3

H2NCH2CH2NH2

NH4+

[2]

(c) Manganese ions, Mn2+(aq), show some similar chemical properties to those of copper(II) ions, Cu2+(aq).

Use this information and the Data Booklet to suggest the formula of the manganese species formed in each of the following reactions. State the type of reaction taking place in each case.

formula of manganesespecies formed

type ofreaction

Mn2+(aq) + NaOH(aq)

Mn2+(aq) + concentrated HCl

Mn2+(aq) + H2O2(aq)

[5]

[Total: 9]

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4 In aqueous solution, 2-chloro-2-methylpropane, (CH3)3CCl, reacts with sodium hydroxide, NaOH. This is a nucleophilic substitution reaction.

(CH3)3CCl (aq) + NaOH(aq) → (CH3)3COH(aq) + NaCl (aq)

(a) Show the mechanism for this reaction. Include all necessary curly arrows, lone pairs and relevant dipoles.

[3]

The rate of this reaction was investigated using a large excess of sodium hydroxide.

(b) The graph below shows the results of the experiment.

0.60

0.50

0.40

0.30

0.20

0.10

00 20 40 60 80 100 120 140 160

time / s

[(CH3)3CCl ]/ mol dm–3

7


The reaction is first order with respect to [(CH3)3CCl ]. This can be confirmed from the graph using half-lives.

(i) What is meant by the half-life of a reaction?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Calculate the half-life for this reaction. Show all your working and show clearly any construction lines on the graph.

[1]

(iii) What would be the effect on the half-life of this reaction if the initial concentration of [(CH3)3CCl ] was doubled?

....................................................................................................................................... [1]

(c) (i) Use the graph in (b) to determine the rate of reaction at 80 s. Show all your working.

rate = ............................. units ............................. [2]

The rate equation for this reaction is shown.

rate = k [(CH3)3CCl ]

(ii) Calculate the value of the rate constant, k, for this reaction and give its units.

k = ............................. units ............................. [1]

[Total: 9]

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5 X is a metallic element.

(a) (i) Draw a fully labelled diagram to show how the standard electrode potential, E o, of X2+(aq) / X(s) could be measured.

[4]

(ii) What are the conditions needed for the value measured to be a standard electrode potential?

....................................................................................................................................... [1]

(iii) State the charge carriers that transfer current through

the solutions, ............................. the wire. ............................. [1]

9


(b) An electrochemical cell was set up consisting of an X2+(aq) / X(s) half-cell (E o = –0.40 V) and an Ag+(aq) / Ag(s) half-cell (E o = +0.80 V).

(i) Write an equation for the reaction that would take place if the electrodes of this cell were connected by a wire.

....................................................................................................................................... [1]

When the current was allowed to pass for a period of time,

• the Ag electrode gained 1.30 g in mass, • the electrode made of metal X lost 0.67 g in mass.

(ii) Calculate the Ar of metal X; hence suggest an identity for X. Show all your working. Use of the Data Booklet is relevant to this question.

Ar = ...........................

X is ...........................[4]

[Total: 11]

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6 Boron forms many useful compounds.

(a) The compound diborane, B2H6, can be used as a rocket fuel. It can be prepared by the reaction of boron trifluoride, BF3, with sodium borohydride, NaBH4.

Balance this equation.

.......BF3 + .......NaBH4 → .......B2H6 + .......NaBF4[1]

(b) Primary and secondary alcohols can be formed by the reaction of carbonyl compounds with NaBH4, which is a source of hydride ions, H–.

Complete the mechanism for the reaction of butanone with hydride ions, H–, and draw the intermediate in the box. Include all necessary curly arrows and relevant dipoles.

CH2CH3

CH2CH3

O

C

intermediate

OH

Cstep 1 H+

H–

H3CH3C

H

[3]

(c) Borane, BH3, is used to synthesise alcohols from alkenes. The reaction occurs in two steps.

The BH2 group from BH3 bonds to the least substituted carbon atom of the double bond, and the remaining H from BH3 bonds to the other carbon.

CH3 H

CH3 CH3

C C

CH3

CH3

H BH2C C+ BH3

Hstep 1 [O]

CH3

CH3

CH3

H OHC C

H

CH3

(i) Suggest the type of reaction in step 1.

....................................................................................................................................... [1]

11


(ii) The diol Y can be prepared by the same method.

CH3

CH3

H3CCH3

OH

OH

Y

Draw the structure of the diene which could be used to prepare diol Y.

[1]

(d) Benzene, C6H6, and borazine, B3N3H6, have planar, cyclic structures.

(i) Describe the structure of and bonding in benzene, C6H6.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) In borazine, B3N3H6, the boron and nitrogen atoms alternate around the ring. Each ring atom has a single hydrogen atom bonded to it.

All boron-nitrogen bonds in borazine are 0.144 nm in length, whereas in simple compounds B–N and B=N bond lengths are 0.154 nm and 0.136 nm respectively.

Suggest and draw the structure of borazine.

[1]

[Total: 10]

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7 (a) Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route.

In step 3 of this synthesis, a phenol-like compound, S, reacts with intermediate T made from amine R.

Assume that the –SO3– Na+ group does not react.

SO3– Na+

SO3– Na+

O2Nstep 1

step 2

+

Sunset Yellow

step 3 NaOH(aq)

R (C6H6NSO3Na)

TS

Q

OH

Na+ –O3S

NN

(i) Suggest structures for compounds R, S and T and draw them in the boxes above. [3]


step 1, .................................................................................................................................

step 2. .................................................................................................................................[3]

(iii) What type of organic salt is formed in step 2?

....................................................................................................................................... [1]

13


(b) Compound W has the following structure.

NH2H2N

O

(i) How many σ and π bonds are present in a molecule of W?

σ bonds ....................... π bonds ....................... [2]

(ii) The products of the reactions of W with cold HCl and with CH3CH2Br are soluble in water but not in organic solvents.

Complete the table for these reactions of W.

reagent structure of product(molecular formula given) type of reaction

HCl

(C4H9N2OCl )

CH3CH2Br

(C6H13N2BrO)

[3]

[Total: 12]

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Section B


8 (a) The sequence of bases in DNA is a code for the order of amino acids in the primary structure of proteins.

The diagram represents the stages involved in the formation of a protein from DNA.

DNA

ribosome protein

A

B2

B1

stage 1

etc.

stage 3

stage 2

(i) Identify the biochemical structures, A and B1, B2 etc.

biochemical structure identity

A

B1, B2 etc.[2]

(ii) Name the biochemical processes involved in stages 1 and 3.

process name of biochemical process

stage 1

stage 3[1]

15


(b) Adenine is an integral part of DNA.

N

N

N

NH2

NH

adenine

(i) State the molecular formula of adenine.

....................................................................................................................................... [1]

(ii) Identify the three other nitrogenous bases in DNA.

..................................... ..................................... ..................................... [1]

(iii) DNA has a double helical structure that consists of two strands linked together.

What type of bonding exists between the

phosphate and sugar groups within a DNA strand, ............................................................

different bases on the two strands? ....................................................................................[2]

(c) The breakdown of adenosine triphosphate, ATP, provides the energy for many cellular reactions.

ATP + H2O → ADP + Pi

What type of chemical reaction is this?

.............................................................................................................................................. [1]

(d) X-ray crystallography can be useful in obtaining information about the structures of large organic molecules, such as ATP. The technique involves X-rays interacting with the electrons within the molecule.

(i) Which element in the molecule of ATP will interact most strongly with the X-ray beam?

....................................................................................................................................... [1]

(ii) Explain why X-ray crystallography will not detect hydrogen atoms.

.............................................................................................................................................

....................................................................................................................................... [1]

[Total: 10]

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9 (a) Some metals are essential to biochemical processes.

Complete the following table naming one metal in each case.

biochemical process metal

haemoglobin in oxygen transport

transmission of nerve impulses

enzyme cofactor[2]

(b) Enzymes are a special type of protein molecule that catalyse biochemical reactions.

Explain briefly the mechanism by which an enzyme breaks down a substrate molecule.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

(c) Disulfide bonds play an important role in the stability of some proteins such as the keratin in human hair.

The amino acid involved in the formation of a disulfide bond is cysteine, H2NCH(CH2SH)CO2H.

(i) At which level of protein structure (primary, secondary, tertiary) are disulfide bonds formed?

....................................................................................................................................... [1]

(ii) Use a functional group in cysteine to show how disulfide bonds are formed.

[1]

(iii) What type of chemical reaction is this?

....................................................................................................................................... [1]

17


(d) The NMR spectrum of cysteine, H2NCH(CH2SH)CO2H, shows five absorptions.

After shaking a solution of cysteine with a few drops of D2O, the NMR spectrum shows only two absorptions, E and F, shown below.

E F

(i) Identify the two types of protons responsible for the absorptions E and F.

E .........................................................................................................................................

F ..........................................................................................................................................[1]

(ii) State and explain the splitting patterns of the absorptions E and F.

E .........................................................................................................................................

.............................................................................................................................................

F .........................................................................................................................................

....................................................................................................................................... [2]

[Total: 11]

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10 (a) Aspartame is an artificial sweetener that has the structure shown below.

aspartame

OH

O

O

O NH2

H3C NH

O

(i) Draw a circle around each chiral centre in aspartame. [1]

In the stomach, aspartame is hydrolysed by acid to form three organic products.

(ii) On the diagram above, use arrows to indicate the two bonds that would be hydrolysed in the stomach. [2]

(iii) Draw the structures of the three products formed after complete acid hydrolysis of aspartame.

[3]

19


(b) Aspartame is soluble in water.

By referring to the structure of aspartame, explain why it is soluble in water.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(c) Recently, nanotechnology has been involved in the development of a new natural sweetener, Nano Sugar, extracted from sugar cane.

What is the approximate width of a nanoparticle?

.............................................................................................................................................. [1]

[Total: 9]

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BLANK PAGE




CHEMISTRY 9701/43


2 hours






*6137146489*








1

2

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Total

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Section A


1 (a) The dissolving of an ionic compound in water is accompanied by an energy change, the enthalpy change of solution, ∆H sol.

MgCl 2(s) + aq → Mg2+(aq) + 2Cl –(aq)

Describe, in terms of bond breaking and bond making, what happens to the solid ionic lattice when an ionic compound dissolves in water.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) (i) What is meant by the term enthalpy change of solution, ∆H sol?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Use the following data to calculate the standard enthalpy change of hydration, , of chloride ions, Cl –(g).

You may find it helpful to construct an energy cycle.


(Mg2+(g)) –1925 kJ mol–1

lattice energy of MgCl 2(s) –2524 kJ mol–1

enthalpy change of solution for MgCl 2(s) –155 kJ mol–1

(Cl –(g)) = ......................... kJ mol–1 [2]

3


(iii) The enthalpy change of hydration for Na+, (Na+(g)), is –410 kJ mol–1.

Suggest an explanation for why the of the Na+ ion is less exothermic than the of the Mg2+ ion.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(c) Describe and explain how the solubility of the Group II sulfates varies down the group.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [4]

[Total: 11]

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2 (a) Cobalt is a transition element and forms compounds with oxidation numbers +2 and +3.

Complete the electronic structures for

a cobalt atom, 1s22s22p6.................................

cobalt in the +3 oxidation state. 1s22s22p6.................................[2]

(b) (i) In an aqueous solution of cobalt(II) sulfate the cobalt forms complex ions.

What is meant by the term complex ion?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) State two chemical properties of cobalt, other than the formation of complexes, that are not shown by a typical s-block element.

.............................................................................................................................................

....................................................................................................................................... [2]

(c) Cobalt(II) ions, Co2+(aq), show some chemical properties similar to those of copper(II) ions, Cu2+(aq).

Use this information and the Data Booklet to suggest the formula of the cobalt species formed in each of the following reactions. State the type of reaction taking place in each case.

formula of cobaltspecies formed type of reaction

Co2+(aq) + an excess of NH3(aq)

Co2+(aq) + OH–(aq)

Co2+(aq) + S2O82–(aq)

[5]

5


(d) Some transition elements are present in superconductors. These are materials that conduct electricity with little or no resistance.

Compound Q is a superconductor and contains 13.4% yttrium, 41.2% barium, 28.6% copper and 16.8% oxygen by mass.

(i) Show that the empirical formula of Q is YBa2Cu3O7. Show all your working.

[1]

(ii) The table shows the oxidation numbers of yttrium, barium and oxygen in Q.

element oxidation number

yttrium +3

barium +2

oxygen –2

Calculate the average oxidation number of copper in Q.

[1]

(iii) Hence deduce the oxidation number of each of the three copper atoms in Q.

[1]

[Total: 13]

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3 Chlorine gas and iron(II) ions react together in aqueous solution as shown.

Cl 2(g) + 2Fe2+(aq) → 2Cl –(aq) + 2Fe3+(aq)

(a) (i) Complete and label the diagram to show how the standard cell potential, , for the above reaction could be measured at standard conditions.

[4]

(ii) Use the Data Booklet to calculate the for this reaction.

[1]

(b) What colour change would you see when chlorine gas is bubbled through a solution containing Fe2+(aq) ions until the reaction is complete?

.............................................................................................................................................. [1]

(c) Predict the effect, if any, of decreasing the concentration of Cl –(aq) on the magnitude of the cell potential in (a)(ii). Explain your answer.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

7


(d) (i) A fuel cell is an electrochemical cell that can be used to generate electrical energy.

In the alkaline hydrogen-oxygen fuel cell, H2(g) and O2(g) are passed over two inert electrodes immersed in an alkaline solution.

Write the half-equations for the reactions taking place at each of these electrodes.

hydrogen electrode .............................................................................................................

oxygen electrode ................................................................................................................[2]

(ii) Construct an equation for the overall reaction.

....................................................................................................................................... [1]

(iii) Suggest one possible advantage of using a hydrogen-oxygen fuel cell over a conventional ‘simple cell’ battery.

....................................................................................................................................... [1]

[Total: 12]

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4 (a) (i) On the grid below, sketch the trend in the melting points of the Group IV elements. The point for germanium has already been shown.

meltingpoint

C Si Ge Sn Pb[1]

(ii) Suggest an explanation of this trend in terms of structure and bonding of the Group IV elements.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

(b) GeO2, SnO2 and PbO2 are amphoteric oxides.

(i) What is meant by the term amphoteric?

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Construct an equation for the reaction of SnO2 with NaOH.

.............................................................................................................................................

....................................................................................................................................... [1]

(c) (i) By quoting information from the Data Booklet explain why the reaction between Cr2O7

2–(aq) ions and acidified Sn2+(aq) ions is feasible.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

9


(ii) Construct an equation for the reaction in (c)(i) and give any relevant observations.

equation ..............................................................................................................................

observations .......................................................................................................................

....................................................................................................................................... [2]

(d) (i) On heating, germanium(II) oxide disproportionates to form germanium(IV) oxide and germanium.

Describe, using this reaction as an example, what is meant by a disproportionation reaction.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Some of the reactions of cyanogen, NC–CN, are similar to those of chlorine, Cl –Cl. On treatment with cold, aqueous sodium hydroxide, cyanogen disproportionates in a

similar manner to chlorine.

Complete the equation for this reaction.

(CN)2 + ........NaOH → .............. + .............. + .............. [1]

(iii) Draw a ‘dot-and-cross’ diagram for NC–CN. Show the outer electrons only.

[1]

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(e) At room temperature, phosphorus atoms form P4 molecules rather than P2 molecules.

The phosphorus molecule, P4, has a cage-like structure containing only P–P single bonds. All the phosphorus atoms in P4 are trivalent.

(i) Suggest a structure for P4.

[1]

(ii) At a temperature of 1200 K P2 and P4 exist in equilibrium in the gas phase.

P2 molecules contain the P≡P bond.

The average bond energy of P–P is 198 kJ mol–1 while that of P≡P is 489 kJ mol–1.

Use the above bond energies to calculate the enthalpy change, ∆H, for the following reaction.

2P2(g) → P4(g)

[2]

(f) When phosphorus(V) chloride, PCl 5, is reacted with ammonium chloride, NH4Cl, hydrogen chloride gas, HCl, is released and a product with the molecular formula P3N3Cl 6 is formed.

(i) Construct an equation for this reaction.

....................................................................................................................................... [1]

(ii) P3N3Cl 6 has a cyclic structure containing alternating phosphorus and nitrogen atoms in the ring system. All the nitrogen atoms are trivalent and all the phosphorus atoms are pentavalent.

Suggest a structure for P3N3Cl 6.

[1]

[Total: 15]

11


TURN OVER FOR QUESTION 5.

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5 (a) A student carries out some reactions with separate samples of butanal and butanone.

H

O

butanal

O

butanone

The following results are obtained with reagents L, M and N. ( means a reaction takes place.)

reagent butanal butanone

L

M no reaction

N no reaction

(i) Suggest a possible identity for each reagent L, M and N.

L ..........................................................................................................................................

M .........................................................................................................................................

N .........................................................................................................................................[3]

(ii) Give the structure of the organic product formed when M reacts with butanal.

[1]

(iii) What is observed when N reacts with butanone?

....................................................................................................................................... [1]

(iv) What type of reaction is occurring when N reacts with butanone?

....................................................................................................................................... [1]

13


(b) The organolithium compound methyl lithium, CH3Li, can act as a source of CH3– ions.

CH3Li CH3– + Li+

The CH3– ion can act as a nucleophile.

The reaction between methyl lithium and carbonyl compounds can be used to make alcohols.

(i) Suggest a mechanism for the reaction of butanal with CH3– ions. Include all necessary

curly arrows, lone pairs and relevant dipoles.

intermediate

step 1 H+

CH3–

CH2CH2CH3CH

O

CH2CH2CH3

CH3

CH

OH

[3]

(ii) A chemist decides to prepare the following organic compound G from butanal.

CH3

CH3

H3C

OH

G

Draw the structure of the organolithium reagent which could be used to prepare G from butanal.

[1]

[Total: 10]

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6 4-nitrophenol can be converted into a range of useful organic products.

OHO2N

4-nitrophenol

(a) 4-nitrophenol can react with three different reagents.

Complete the table by:

• drawing the structures of the organic products formed, • identifying the non-organic products formed.

reagent organic product structure identity ofnon-organic product

Na(s)

Br2(aq)

CH3COCl (l)

[4]

15


(b) 4-nitrophenol can also be used in the synthesis of the dye Mordant Brown by the following route.

In step 2 of this synthesis, 4-nitrophenol reacts with intermediate F made from amine E. Assume that the –SO3

– Na+ group does not react.

+

OH

NO2

E (C6H8N3SO3Na)

F

step 1

step 2

OH

NO2

N N SO3– Na+

H2N NH2

Mordant Brown

(i) Suggest structures for compounds E and F and draw them in the boxes above. [2]


step 1, .................................................................................................................................

step 2. .................................................................................................................................[3]

[Total: 9]

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Section B


7 DNA is an important biochemical molecule.

(a) DNA has a double helical structure that consists of two strands linked together.

Draw a block diagram of DNA showing two repeat units in each strand. Label all the components, showing and labelling the bonds between the strands.

[5]

(b) Genetic information is stored in DNA.

Outline the main steps in the replication of DNA.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

17


(c) DNA fingerprinting is based on the fact that all humans (apart from genetically identical twins) have different DNA base sequences. This is regularly used to help investigate serious crimes.

(i) The first stage of DNA fingerprinting requires a sample of DNA to be broken down into shorter fragments.

What could be used to carry out this fragmentation?

....................................................................................................................................... [1]

(ii) Name the analytical technique used to separate these short fragments.

....................................................................................................................................... [1]

(iii) After the fragments have been separated, what could the DNA fingerprint be treated with to reveal the position of the bands?

....................................................................................................................................... [1]

(iv) A sample of blood, thought to be from the suspect, was found at a crime scene. The DNA of the blood sample, and that of four possible suspects, was analysed.

bloodstain

suspect1

suspect2

suspect3

suspect4

Based on this evidence, circle the suspect who should be arrested.

suspect 1 suspect 2 suspect 3 suspect 4

[1]

[Total: 11]

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8 (a) A mixture of volatile organic compounds X, Y and Z can be separated in a gas chromatograph. Their identities can be confirmed by measuring their different retention times and comparing to

known values. A gas chromatogram is shown.

absorptionX

Y

Z

5 10 15 20time / mins

(i) Suggest what is meant by the term retention time.

.............................................................................................................................................

....................................................................................................................................... [1]

(ii) Give an example of a carrier gas used in gas chromatography.

....................................................................................................................................... [1]

(iii) Z spends the longest time in the chromatography column.

Suggest why this might be the case.

.............................................................................................................................................

....................................................................................................................................... [1]

(iv) Explain a possible limitation of gas / liquid chromatography in separating two esters such as ethyl methanoate, HCO2CH2CH3, and methyl ethanoate, CH3CO2CH3.

.............................................................................................................................................

....................................................................................................................................... [1]

(v) A student works out the areas underneath the three peaks in the chromatogram.

peak X Y Z

area / mm2 22 38 16

Assuming the areas underneath the peaks are proportional to the masses of the respective components, what percentage of the original mixture was made up of the organic compound, X?

% of X = ........................ [1]

19


(b) The NMR spectrum of Y given below shows four absorptions.

absorption

4 3 2δ / ppm

1 0

(i) What compound is responsible for the absorption at δ = 0?

....................................................................................................................................... [1]

(ii) Compound Y is an ester with the molecular formula C4H8O2.

Complete the table for the NMR spectrum of Y. The actual chemical shifts for three absorptions in Y and the splitting pattern for the

resonance at δ = 3.7 ppm have been given for you. Use of the Data Booklet may be helpful.

chemical shiftδ / ppm type of proton(s) number of protons splitting pattern

1.0

2.3

3.7 singlet

[4]

(iii) Use your conclusions to suggest a structure for the ester Y.

[1]

[Total: 11]

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9 Prodrugs are compounds that are inactive, but are easily converted in the body to the active drug by enzyme hydrolysis.

Compound W is a prodrug.

O

OO

NH2H2N

CH3

W

(a) Complete the molecular formula for W.

C H34N O[1]

(b) Compound W contains a benzene ring in its structure.

Name three other functional groups in W.

.......................................... .......................................... .......................................... [2]

(c) (i) On the diagram above, use an arrow to indicate the bond that would be hydrolysed. [1]

(ii) Draw the structures of the likely products of the enzyme hydrolysis of compound W.

[2]

(d) What features of the molecule W make it water soluble? Explain your answer.

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 8]





CHEMISTRY 9701/51

Paper 5 Planning, Analysis and Evaluation October/November 2015

1 hour 15 minutes


No Additional Materials are required.




*3961515302*

2

9701/51/O/N/15© UCLES 2015

1 It is possible to determine the relative molecular mass, Mr, of a small sample of a volatile liquid by measuring its mass and then heating to vaporise it to obtain its volume as a gas.

(a) Explain how the relative molecular mass can be determined in this way.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) (i) The volume of the vaporised sample depends on its temperature and pressure.

In an experiment, a sample of volatile liquid of known mass was vaporised and its volume recorded. The pressure was correctly recorded as 101 kPa but the temperature was incorrectly recorded as 50 °C. The correct temperature was 60 °C.

By considering the effect of these different temperatures on the gas volume, explain how the value of the calculated Mr would be affected.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) The temperature was maintained at 60 °C but the pressure was increased to 110 kPa. Would this have given an answer that was nearer to the true value of the relative molecular mass? Explain your answer.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

3


In an experiment to determine the relative molecular mass of hexane, boiling point 69 °C, a specialist piece of apparatus called a Victor Meyer tube can be used. This consists of a long tube with a bulb at the base in which a sample can be vaporised. The tube has a side arm to allow the escape of gas from within the tube. The tube is surrounded by another which can be used to heat the contents of the fi rst tube.

A diagram of the apparatus is shown below.

Victor Meyer tube

sand

stopper

smallsample tube

hexane

A small sample tube containing the hexane is inserted at the top of the Victor Meyer tube. The sample tube is small enough to fi t inside the Victor Meyer tube and falls freely onto the hot sand below. The sand will cushion its fall so that the sample tube does not break. The stopper is then quickly replaced at the top of the Victor Meyer tube. The hot sand causes the hexane to vaporise and expel air contained in the Victor Meyer tube.

(c) Complete the diagram above to show:

● how the apparatus should be heated,

● a connection to further apparatus which would allow the air expelled from the Victor Meyer tube when the sample of hexane is vaporised to be collected and measured.

[2]

(d) Suggest one hazard associated with the use of hexane.

....................................................................................................................................................

.............................................................................................................................................. [1]

4

9701/51/O/N/15© UCLES 2015

(e) (i) With the gas collection apparatus connected to the heated Victor Meyer tube, expelled air will be collected before the hexane is introduced. Explain why.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) At which stage of the experimental procedure should the sample tube be dropped into the Victor Meyer tube?

.............................................................................................................................................

....................................................................................................................................... [1]

(f) State what measurements you would need to make in order to determine the relative molecular mass of hexane.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 15]

5


QUESTION 2 STARTS ON THE NEXT PAGE.

6

9701/51/O/N/15© UCLES 2015

2 In an experiment, various masses of solid barium hydroxide are added to 60.0 cm3 of a solution of hydrochloric acid contained in a polystyrene cup.

In each experiment a fresh sample of the acid is taken and its initial temperature is measured. After the barium hydroxide has been added, the acid is stirred and the maximum temperature reached is noted.

The results of each experiment are recorded in the table below.

(a) Complete the table below to give the temperature rise obtained from each experiment to one decimal place and the amount of barium hydroxide used in mol to three signifi cant fi gures in each case.

The mass of 1 mol of barium hydroxide is 171 g.

initial temperature of HCl / °C

mass ofbarium hydroxide

added /g

maximum temperature reached / °C

temperaturerise / °C

barium hydroxide added / mol

21.0 0.500 22.2

20.6 1.00 23.0

21.2 1.50 24.9

21.8 2.00 26.5

20.5 3.00 27.8

21.4 4.00 31.1

21.2 5.00 31.6

21.0 6.00 31.4

20.8 8.00 31.2

[2]

(b) (i) Using the grid on page 7, plot a graph to show how the temperature rise varies with the moles of barium hydroxide added. [1]

7


0.000 0.010 0.020


tem

pera

ture

rise

/ °C

0.030 0.040 0.050

12.0

11.0

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

(ii) Draw two lines of best fi t on your graph and state the value on the x-axis at the point of intersection of the two lines.

value on the x-axis at the point of intersection is .................................... [2]

8

9701/51/O/N/15© UCLES 2015

(c) Use the value on the x-axis at the point of intersection to calculate the concentration of the hydrochloric acid in mol dm–3.

[2]

(d) Explain the variation in temperature that takes place when barium hydroxide is added to the hydrochloric acid.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(e) (i) When the experiment is done in the way described, the results are not very accurate.

Apart from limitations due to the accuracy of the measuring equipment, suggest why:

● all the temperature rises measured are less than theoretically should be expected,

.............................................................................................................................................

.............................................................................................................................................

● the temperature rises are more inaccurate as they approach their maximum value.

.............................................................................................................................................

.............................................................................................................................................[2]

(ii) What improvement would you make to achieve greater accuracy?

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

9


(f) In another experiment, 60.0 cm3 of ethanoic acid is used instead of the 60.0 cm3 of hydrochloric acid.

If the ethanoic acid has the same concentration as the hydrochloric acid, draw on your graph another pair of lines to show the results you would expect to obtain.


....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 15]

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CHEMISTRY 9701/52


1 hour 15 minutes






*4704348548*

2

9701/52/O/N/15© UCLES 2015

1 It is possible to determine the relative molecular mass, Mr, of a small sample of a volatile liquid by measuring its mass and then heating to vaporise it to obtain its volume as a gas.

(a) Explain how the relative molecular mass can be determined in this way.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(b) (i) The volume of the vaporised sample depends on its temperature and pressure.

In an experiment, a sample of volatile liquid of known mass was vaporised and its volume recorded. The pressure was correctly recorded as 101 kPa but the temperature was incorrectly recorded as 50 °C. The correct temperature was 60 °C.

By considering the effect of these different temperatures on the gas volume, explain how the value of the calculated Mr would be affected.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(ii) The temperature was maintained at 60 °C but the pressure was increased to 110 kPa. Would this have given an answer that was nearer to the true value of the relative molecular mass? Explain your answer.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

3


In an experiment to determine the relative molecular mass of hexane, boiling point 69 °C, a specialist piece of apparatus called a Victor Meyer tube can be used. This consists of a long tube with a bulb at the base in which a sample can be vaporised. The tube has a side arm to allow the escape of gas from within the tube. The tube is surrounded by another which can be used to heat the contents of the first tube.

A diagram of the apparatus is shown below.

Victor Meyer tube

sand

stopper

smallsample tube

hexane

A small sample tube containing the hexane is inserted at the top of the Victor Meyer tube. The sample tube is small enough to fit inside the Victor Meyer tube and falls freely onto the hot sand below. The sand will cushion its fall so that the sample tube does not break. The stopper is then quickly replaced at the top of the Victor Meyer tube. The hot sand causes the hexane to vaporise and expel air contained in the Victor Meyer tube.

(c) Complete the diagram above to show:

● how the apparatus should be heated,

● a connection to further apparatus which would allow the air expelled from the Victor Meyer tube when the sample of hexane is vaporised to be collected and measured.

[2]

(d) Suggest one hazard associated with the use of hexane.

....................................................................................................................................................

.............................................................................................................................................. [1]

4

9701/52/O/N/15© UCLES 2015

(e) (i) With the gas collection apparatus connected to the heated Victor Meyer tube, expelled air will be collected before the hexane is introduced. Explain why.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) At which stage of the experimental procedure should the sample tube be dropped into the Victor Meyer tube?

.............................................................................................................................................

....................................................................................................................................... [1]

(f) State what measurements you would need to make in order to determine the relative molecular mass of hexane.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 15]

5


QUESTION 2 STARTS ON THE NEXT PAGE.

6

9701/52/O/N/15© UCLES 2015

2 In an experiment, various masses of solid barium hydroxide are added to 60.0 cm3 of a solution of hydrochloric acid contained in a polystyrene cup.

In each experiment a fresh sample of the acid is taken and its initial temperature is measured. After the barium hydroxide has been added, the acid is stirred and the maximum temperature reached is noted.

The results of each experiment are recorded in the table below.

(a) Complete the table below to give the temperature rise obtained from each experiment to one decimal place and the amount of barium hydroxide used in mol to three significant figures in each case.

The mass of 1 mol of barium hydroxide is 171 g.

initial temperature of HCl / °C

mass ofbarium hydroxide

added /g

maximum temperature reached / °C

temperaturerise / °C


21.0 0.500 22.2

20.6 1.00 23.0

21.2 1.50 24.9

21.8 2.00 26.5

20.5 3.00 27.8

21.4 4.00 31.1

21.2 5.00 31.6

21.0 6.00 31.4

20.8 8.00 31.2

[2]

(b) (i) Using the grid on page 7, plot a graph to show how the temperature rise varies with the moles of barium hydroxide added. [1]

7


0.000 0.010 0.020


tem

pera

ture

rise

/ °C

0.030 0.040 0.050

12.0

11.0

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

(ii) Draw two lines of best fit on your graph and state the value on the x-axis at the point of intersection of the two lines.

value on the x-axis at the point of intersection is .................................... [2]

8

9701/52/O/N/15© UCLES 2015

(c) Use the value on the x-axis at the point of intersection to calculate the concentration of the hydrochloric acid in mol dm–3.

[2]

(d) Explain the variation in temperature that takes place when barium hydroxide is added to the hydrochloric acid.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(e) (i) When the experiment is done in the way described, the results are not very accurate.

Apart from limitations due to the accuracy of the measuring equipment, suggest why:

● all the temperature rises measured are less than theoretically should be expected,

.............................................................................................................................................

.............................................................................................................................................

● the temperature rises are more inaccurate as they approach their maximum value.

.............................................................................................................................................

.............................................................................................................................................[2]

(ii) What improvement would you make to achieve greater accuracy?

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [1]

9


(f) In another experiment, 60.0 cm3 of ethanoic acid is used instead of the 60.0 cm3 of hydrochloric acid.

If the ethanoic acid has the same concentration as the hydrochloric acid, draw on your graph another pair of lines to show the results you would expect to obtain.


....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 15]

10

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CHEMISTRY 9701/53


1 hour 15 minutes






*6297643386*

2

9701/53/O/N/15© UCLES 2015

1 The halogenoalkanes can react with hydroxide ions to form an alcohol and a halide ion.

(a) The rate at which the reaction occurs depends on which of the halogenoalkanes is chosen. The reaction is a nucleophilic attack by the hydroxide ion and the rate might depend on:

● the polarity of the carbon-halogen bond,

● the bond strength of the carbon-halogen bond.

For (i) and (ii), chlorobutane, bromobutane and iodobutane should be considered.

(i) If the rate of reaction was only controlled by the polarity of the carbon-halogen bond, the order of reactivity (most reactive to least reactive) would be

........................................................................................................................................... .

Explain the variation in the polarity of the carbon-halogen bonds.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

(ii) If the rate of reaction was only controlled by the bond strength of the carbon-halogen bond, the order of reactivity (most reactive to least reactive) would be

........................................................................................................................................... .

Explain the variation in the bond strength of the carbon-halogen bonds.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[2]

3


(b) An experiment can be carried out to compare the extent of the reaction between aqueous hydroxide ions and chlorobutane, bromobutane and iodobutane. Samples of the halogenoalkanes are reacted with sodium hydroxide for 2 minutes at 50 °C. After the reaction, addition of aqueous silver nitrate causes the formation of a silver halide precipitate.

Some hazards associated with the use of halogenoalkanes include:● very hazardous in case of skin and particularly eye contact,● very hazardous if inhaled or ingested,● fl ammable.

To carry out this experiment, the following would be supplied.

● usual laboratory apparatus ● laboratory reagents including a suitable aqueous solution of sodium hydroxide and

aqueous silver nitrate ● samples of each of the three liquid halogenoalkanes

(i) Identify the independent variable and the dependent variable in this experiment.

independent variable ..........................................................................................................

dependent variable .............................................................................................................[1]

(ii) The amount of each halogenoalkane liquid to use is most practically measured by its volume. Usually equal volumes of the three halogenoalkanes are used.

Explain why this is not ideal and what change should be made to obtain a more reliable comparison between the halogenoalkanes.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

4

9701/53/O/N/15© UCLES 2015

(iii) Answer the following questions about the experiment.

● Having measured the quantity of halogenoalkanes, what must be ensured about the amount of sodium hydroxide used?

.............................................................................................................................................

.............................................................................................................................................

● How would the reaction tubes be heated and the experiment be started?

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

● What reagent could be added which would ensure that after 2 minutes the reaction was stopped?

.............................................................................................................................................

.............................................................................................................................................

● After the reaction has been stopped and aqueous silver nitrate added, the amount of precipitate formed could be determined by measuring its height.

Why is it necessary to leave the tubes for some time before making this measurement?

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................[5]

(iv) Although the amount of silver halide formed can reasonably be obtained by measuring the height of the precipitate in the reaction tube, this is not very reliable.

Explain what should be done with the precipitate to obtain a more reliable measurement of the amount of silver halide produced.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

5


(c) The use of halogenoalkanes is hazardous and both gloves and eye protection are necessary. State one other essential precaution which should be taken when carrying out the experiments.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [1]

[Total: 15]

6

9701/53/O/N/15© UCLES 2015

2 At 25 °C, dinitrogen tetroxide, N2O4(g), forms an equilibrium mixture with nitrogen dioxide, NO2(g).

N2O4(g) 2NO2(g) ∆H = +57.2 kJ mol−1

As N2O4(g) is colourless and NO2(g) is brown, the composition of an equilibrium mixture can be determined by its colour.

(a) Write an expression for the equilibrium constant, Kc, for this equilibrium.

[1]

(b) In an experiment, quantities of N2O4 are left to reach an equilibrium which contains N2O4 and NO2. These are analysed to determine the concentrations of N2O4(g) and NO2(g) that are present. The results are listed in the fi rst two columns of the table below.

Complete the third column of the table to give the value of [NO2(g)]2 for each of the results of the experiment. Values should be given to three signifi cant fi gures.

[N2O4(g)] / mol dm–3 [NO2(g)] / mol dm–3 [NO2(g)]2 / mol2 dm–6

0.900 0.0729

0.800 0.0687

0.700 0.0643

0.600 0.0595

0.500 0.0548

0.400 0.0486

0.300 0.0390

0.200 0.0344

0.100 0.0243[2]

(c) (i) The value of the equilibrium constant for N2O4(g) 2NO2(g) can be calculated from a graph of [N2O4(g)] against [NO2(g)]2.

Use the grid on page 7 to plot this graph and draw a line of best fi t through the plotted points.

7


0.00 0.10 0.20 0.30 0.40 0.50[N2O4(g)] / mol dm–3

[NO

2(g)

]2 / mol

2 dm

–6

0.60 0.70 0.80 0.90

0.006

0.005

0.004

0.003

0.002

0.001

0.000

[2]

8

9701/53/O/N/15© UCLES 2015

(ii) Choose two suitable sets of values from your graph and use them to calculate a value for the equilibrium constant, Kc. Give your answer to three signifi cant fi gures and give its units.

co-ordinates of two points used ......................................... .........................................

Kc = ........................ units ........................[3]

(d) Identify the result which is most anomalous and suggest a reason, other than a calculation error, why this may have occurred.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

.............................................................................................................................................. [2]

(e) (i) On your graph, draw a line that would be obtained if the temperature of the equilibrium mixture was raised. [1]

(ii) Explain the position of the line drawn in (i).

.............................................................................................................................................

....................................................................................................................................... [1]

(iii) What effect, if any, would the higher temperature have on the value of Kc?

.............................................................................................................................................

....................................................................................................................................... [1]

(iv) How would your value for the equilibrium constant change if the pressure applied to the equilibrium mixture was increased?

....................................................................................................................................... [1]

9


(f) In the experiments, the results have been obtained by starting with pure N2O4(g) and then letting the equilibrium with NO2(g) form.

Calculate the starting concentration of pure N2O4(g) that would be required to produce the mixture of 0.900 mol dm–3 of N2O4(g) and 0.0729 mol dm–3 of NO2(g) once equilibrium had been established.

[1]

[Total: 15]

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