KIMIA SET 3 Perfect Score

Set 3 Chemistry Perfect Score Module 2007

1

PAPER 2: STRUCTURE QUESTIONS

SECTION A

1 The table below shows the description and observation for two experiments involving two solutions:

Hydrogen chloride in solvent X Hydrogen chloride in solvent Y

Experiment DescriptionObservation

HCl in solvent X HCl in solvent Y

IReaction of hydrogen chloridein solvent X and solvent Y withcalcium carbonate lumps.

Effervescence occurs.A colourless gas isliberated.

No change occur

IIElectrolysis of hydrogenchloride in solvent X andsolvent Y

Ammeter showsreading

Ammeter does notshow reading.

(a) Name a suitable compound for

Solvent X : ....................................................................................................................................

Solvent Y: .....................................................................................................................................

[2 marks]

(b) (i) Which of the solution shows acidic properties?

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

(ii) What is the role of solvent in (b) (i) that enables the solution to show acidic properties?

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

(c) (i) Effervescence occurs when hydrogen chloride in solvent X react with calciumcarbonate. Name the gas liberated.

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

(ii) Describe a chemical test to identify the gas liberated in (c) (i)

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

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

(iii) Write ionic equation for the reaction in (c) (i).

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

[4 marks]

(d) Hydrogen chloride in solvent X can conduct electricity but hydrogen chloride in solvent Y cannotconduct electricity. Explain why.

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

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

[2 marks]


2

(e) Calculate the mass of hydrogen chloride gas, HCl to prepare 100 cm3

of 0.5 mol dm-3

HCl acid.[Given that the relative atomic mass of H = 1, Cl = 35.5 , C = 12, Ca = 40 , O = 16 ]

[3 marks]

2 The diagram shows the set up apparatus for the titration of sodium hydroxide solution with hydrochloric acid.

1.0 moldm-3

hydrochloric acid is added to 25 cm3

of 1.0 moldm-3

sodium hydroxide solution andphenolphthalein is used as an indicator .

a) (i) Name the reaction between sodium hydroxide solution and hydrochloric acid.

…………………………………………………………………………………………………………………………[ 1 mark ]

(ii) Name the salt produced in the experiment.

…………………………………………………………………………………………………………………………[ 1 mark ]

(b) State the colour change in the conical flask at the end point.

…………………………………………………………………………………………………………………………[ 1 mark]

(c) Write a chemical equation for the reaction occurs in the conical flask.

…………………………………………………………………………………………………………………………[ 1 mark]

(d) (i) Calculate the volume of 1.0 moldm-3

hydrochloric acid needed to exactly neutralise 25 cm3

of 1.0moldm

-3sodium hydroxide solution.

[2 marks ]

Hydrochloric acid1moldm

-3

50 cm3

of 1 moldm-3

sodium hydroxidesolution andphenolphthalein

Set 3 Chemistry Perfect Score Module 2007(ii) The experiment above is repeated by replacing 1.0 moldm

-3hydrochloric acid with 0.5 moldm

-3

sulphuric acid. Predict the volume of sulphuric acid required to complete neutralise the sodiumhydroxide solution.

……………………………………………………………………………………………………………….......[ 2 marks ]

(e) Calculate the maximum mass of the salt formed in this experiment.[Given that the relative atomic mass of Na = 23, Cl = 35.5 ]

[ 2 marks ](f) State one of the uses of the salt formed in daily lives.

…………………………………………………………………………………………………………………………[ 1 mark ]

3 The diagram shows series of reactions for the preparation of copper(II) chloride from copper(II)carbonate.

Based on the diagram,(a) (i) name the solid X

………………………………………………………

(ii) suggest how to change copper(II) carbonate t

………………………………………………………

(iii) explain how gas Y is identified.

………………………………………………………

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

Copper(II) carbonate

Co

Step I
Solid X Colourless gas Y
Step IIExcess solid X is added to dilutehydrochloric acid

+

3

…………………………………………………………………[ 1 mark ]

o solid X in step I.

…………………………………………………………………[ 1 mark ]

…………………………………………………………………

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

Solution R

pper(II) chloride

Step III

Set 3 Chemistry Perfect Score Module 2007(iv) Draw a labelled diagram of the apparatus that you can use to produce solid X and identify gas Y

in step I.

[ 2 marks]

(b) (i) Why is excess of solid X added to the heated dilute hydrochloric acid in step II?

…………………………………………………………………………………………………………………………[ 1 mark ]

(ii)Write the chemical equation for the reaction in step II.

…………………………………………………………………………………………………………………………[ 1 mark ]

(c) Describe how copper(II) chloride crystals are obtained from solution R in step III.

…………………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………………[ 3 marks ]

4 The diagram shows the formation of lead(II) nitrate and its changes to other compounds.

Lead(II) nitrate Brown gas
Lead(II) oxide
(a) (i) Lead(II)

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

(ii) Write the

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

+ compound J

4

oxide has reacted with compoun

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

chemical equation for the react

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

Compound Z cop

d J to form lead(II) nitrate. Name compound J

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

ion in (a) (i)

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

+ copper(II) chloride solution

per(II) nitrate

Set 3 Chemistry Perfect Score Module 2007(b) (i) Name the brown gas.

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

(ii) Write the chemical equation for the reaction in (b) (i)

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

(c) When copper(II) chloride solution is added to lead(II) nitrate solution, a precipitate Z andcopper(II) nitrate are produced.

(i) Name the type of reaction occurs.

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

(ii) Write the ionic equation for the formation of compound Z.

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

(iii) State how compound Z is separated from copper(II) nitrate.

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

(d) Sodium hydroxide solution is added a little at a time to lead(II) nitrate solution until in excess.What is the observation?

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

5 10.0 cm³ of 1.0 mol dm-3 sodium iodide is poured to 8 different test tubes. Different volume of 1.0

moldm-3 lead(II) nitrate are added to each test tube. The height of precipitate formed in each test tubeis measured.

The graph below is obtained when the height of precipitate is plotted against the volume of lead(II)nitrate solution.

(a) Na

....

Height ofprecipitate/cm

5

1 2 3 4 5 6 7 8

me the precipitate formed.

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

5

Volume of lead(II)nitrate /cm

3


6

(b) 10 cm3

of 1.0 mol dm-3 lead(II) nitrate is added to 1.0 mol dm-3 sodium iodide solution.Estimate the height of the precipitate formed.

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

(d) Based on the above graph, what is the volume of lead(II) nitrate needed to completely reactwith sodium iodide solution?

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

(e) Calculate(i) the number of moles of potassium iodide in the reaction.

[ 1 mark ](ii) the number of moles of lead(II) nitrate that has completely reacted with potassiumiodide solution.

[ 1 mark ](f) Write the ionic equation for the formation of the precipitate.

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

(g) The concentration of lead(II) nitrate is changed from 1.0 mol dm-3 to 2.0 mol dm-3 . Sketch thegraph obtained on the above graph.

[ 1 mark](h) The mixture in test tube 8 is filtered. State the observation when the sodium hydroxide solution

is added to the filtrate until in excess .

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

………………………………………………………………………………………….............................[ 2 marks ]

6 An experiment is carried out to study the decomposition of 25 cm3

of hydrogen peroxide at roomtemperature with the presence of manganese (IV) oxide as a catalyst.

The results of the experiment are shown below.:

Time/ s 0 30 60 90 120 150 180

Volume of gas/cm

3 0 17 29 34 36 36 36

(a) Write the balance equation for the decomposition of hydrogen peroxide with the presence of catalyst.

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

[1 mark]


7

(b) Draw a graph of volume of gas against time for the reaction.

[3 marks

(c) Based on the graph in (b), calculate(i) the average rate of reaction in the first minute

[1 mark]

(ii) the rate of reaction at 60 seconds.

[2 marks](d) Based on the volume of oxygen gas released, calculate the concentration of hydrogen peroxide in the

experiment..(1 mol of gas occupies 24 000 cm

3at room temperature and pressure)

[2 marks]

(e) The rate of decomposition of hydrogen peroxide is very low.Based on the collision theory, explain how the presence of catalyst increases the rate of decompositionof hydrogen peroxide.

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

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

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

[3 marks]

7 An experiment is carried out to determine heat of displacement for the reaction between 50 cm3

of0.1moldm

-3copper(II) sulphte solution and zinc powder. AN excess of zinc powder is added to the

copper(II) sulphate solution in a polystyrene cup.

The results of the experiment are shown below.:

Initial temperature /0C 28.2

Maximum temperature /0C 33.4

[Specific heat capacity of solution = 4.2 J g-1 0

C-1

]

(a) What is meant by heat of displacement in the experiment?

……………………………………………………………………………………………………………….[ 1 mark ]

(b) State another observation besides the change in temperature.

……………………………………………………………………………………………………..………..[ 1 mark ]

Set 3 Chemistry Perfect Score Module 2007(c) Calculate

(i) The heat released in the experiment.

[ 1 mark ]

(ii) The number of moles of copper(II) sulphate that has reacted with copper.

[ 1 mark ](iii) Heat of displacement .

[ 2 marks ](d) Construct energy level diagram for the reaction .

[ 2 marks ]

(i) Polystyrene cup A is used in the experiment . The experiment is repeated using cup B.Predict the change in temperature. Explain your answer.

Prediction:

……………………………………

Explanation:

……………………………………

……………………………………

Cup A

Polystyrene

8

………………………………………………………………………….[ 1 mark ]

…………………………………………………………......................

…………………………………………………………......................[ 2 marks ]

cup

Cup B


9

PAPER 2 – ESSAY SECTION B SECTION C

8 (a) Table 10.1 shows the results of an experiment to study the role of water in showing the acidicproperties.

State of acid ObservationGlacial ethanoic acid Cannot conduct electric current

Aqueous solution of ethanoic acid Can conduct electric current

TABLE 10.1

Explain why the observations in Table 10.1 are different. [5 marks ]

(b) Table 10.2 shows the results of an experiment to compare the strength of acids.

TABLE 10.2

Explain why the pH values of hydrochloric acid and ethanoic acid in Table 10.2 are different.[ 5 marks]

(c) (i) State three preparation method of soluble salts.(ii) Zinc chloride is a soluble salt. Describe how to prepare zinc chloride crystals from zinc

carbonate.

[10 marks]

Acid pH valueHydrochloric acid of 0.1 mol dm

-31

Ethanoic acid of 0.1 mol dm-3

4


10

9 (a) What is effective collisions? [ 2 marks ]

(b) An experiment is carried out to study the rate of reaction between magnesium strip and different type ofacids.The time taken by magnesium strip to dissolve in acids in each experiment is recorded in Table 11.

Experiment Reactant Temperature(0C)

Time(s)

I 20 cm3

of 1.0 moldm-3

ethanoic acid +15 cm of magnesium strip

30 150

II 20 cm3

of 1.0 moldm-3

hydrochloric acid +15 cm of magnesium strip

30 60

III 20 cm3

of 1.0 moldm-3

sulphuric acid +15 cm of magnesium strip

30 30

IV 20 cm3

of 1.0 moldm-3

hydrochloric acid +15 cm of magnesium strip +5 drops of copper(II) sulphate solution

30 42

TABLE 11(i) Write an ionic equation for the reaction between magnesium strip and acid. [ 1 mark ]

(ii) Compare the rate of reaction for experiment I and experiment II, experiment II and experiment III. experiment II and experiment IV

Explain your answer based on the collision theory.[ 8 marks ]

(ii) If experiment II is repeated at 400C, predict the time taken for the 15 cm magnesium strip to

dissolve completely. Explain your answer..[ 3 marks ]

(c) Explain why

(i) food stored in the refrigerator lasts longer than food stored in the kitchen cabinet.[ 3 marks ]

(ii) meat cut into small pieces can be cooked faster compare with meat in big chunks.[ 3 marks ]


11

10 Three experiments have been carried out to study the effect of factors affecting the rate of reaction atroom temperature. Table 12 shows the results of the experiments.

Experiment I II III

Set-up ofapparatus

Time takenformagnesiumstrip to reactcompletely(s)

60 30 10

i) Write the chemical equation for the reaction between magnesium and sulphuric acid.Calculate the maximum volume of gas released in experiment I and experiment II.[Molar volume: 24 dm

3mol

-1at room condition]

[6 marks]

ii) Using the same axis on the graph, sketch the volume of gas released against time forExperiment I, II and III. [3 marks]

iii) Calculate the average rate of reaction for Experiment I, II and III in cm3

s-1

.[3 marks]

iv) Compare the rate of reaction for Experiment I and Experiment II; Experiment II and Experiment III.

For each of the above cases, explain why there is a difference in the rate of reaction based onthe collision theory.

[8 marks]

10 cm3

of1 mol dm

-3

sulphuric acid

Excess ofmagnesiumstrip

10 cm3

of2 mol dm

-3

sulphuric acid

Excess ofmagnesiumstrip

Excess ofmagnesiumpowder

10 cm3

of2 mol dm

-3

sulphuric acid


12

11 (a) Name a soluble salt and an insoluble salt.

Write a chemical equation for the preparation of each type of salt given by you.[4 marks]

(b) You are given zinc nitrate crystals. Describe how you can perform a chemical test to confirm thepresence of zinc ions and nitrate ions in the zinc nitrate crystals.

[6 marks]

(c) You are required to prepare magnesium nitrate salt from the chemical substances provided below.

Your answer should include all the chemical equations involved in the reactions.[10 marks]

12 (a) The cooking of food in a pressure cooker can save energy and time compared to the normal cooker.Explain why. [2 marks]

(b) Catalysts are very important in industrial processes as they save energy, labour and time by increasingthe rate of chemical reaction.Name a chemical process in industry and the catalyst used in the process.

[2 marks](c) The size of solid reactant can affect the rate of reaction.

Describe an experiment to investigate the effect of the size of solid reactant on the rate of reaction.Your answer must include the diagram of the set-up of apparatus used in the experiment.

[16 marks]

13 (a) What is heat of neutralisation?[ 1 mark ]

(b) Table 15 shows the values of heat of reaction between different types of acids and alkalis.

ReactionChemical equation

Heat ofreaction

I NaOH(aq) +HCl(aq)→ NaCl(aq) + H2O(l) 57 kJ

II KOH(aq) +HNO3(aq) → KNO3(aq) + H2O(l) 57 kJ

III 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + H2O(l) 114kJ

IV NaOH(aq) + CH3COOH(aq) → CH3COONa(aq)+H2O(l)

55kJ

Explain why heat of reaction I equal to heat of reaction II heat of reaction III is double the heat of reaction I heat of reaction IV is less than heat of reaction I heat of neutralisation of reaction III is 57kJmol

-1and not 14kJmol

-1.

[ 7 marks ](c) Describe an experiment to determined the heat of neutralisation between dilute hydrochloric

acid and sodium hydroxide solution. You must include the calculation and precautions that needto be taken.

[ 12 marks ]

Magnesium sulphate solution Dilute nitric acid Sodium carbonat solution

Set 3 Chemistry Perfect Score Module 2007Paper 3

14 A student carried out an experiment to investigate the relationship between concentration of acid with pHvalue. The acid used is a strong acid which is hydrochloric acid. A standard solution of 250 cm

3

hydrochloric acid with concentration of 1.0 mol dm-3

was prepared.. The acid solution is then diluted to givethree acid solutions with different concentrations. pH value of the three solutions is determined by a pHmeter. The pH value for each solution is recorded in the table below.

Concentration of acid/moldm-3

0.1 0.01 0.001 0.0001pH value 1.0 2.1 3.2 4.1

(a) State the hypothesis of the experiment.

…………………………………………………………………………………………………………………(b) Why does the pH value of hydrochloric acid increase when the concentration decreases?

…………………………………………………………………………………………………………………

(c) The student continued the experiment by carrying out a titration process using the hydrochloric acid standardsolution to determine the unknown concentration of a sodium hydroxide solution. 25 cm

3of sodium

hydroxide solution is poured into a conical flask. Three drops of phenolphtalein is added to the sodiumhydroxide solution. The solution is then titrated with hydrochloric acid 0.1 mol dm

-3from a burette. The

titration process is carried out until the end point is obtained. Initial and final burette reading for the threetitrations carried out are shown in the Diagram below.

(i)

Initialreading

Finalreading

Initialreading

Finalreading

Initialreading

Finalreading

Based on the diagram ab

Number of titrationsFinal reading/cm

3

Initial reading/cm3

Volume of hydrochloricacid solution used/cm

3

Titration 1

13

ove, complete the table below.

1 2 3

Titration 2 Titration 3

Set 3 Chemistry Perfect Score Module 2007(ii) What is the average volume of the hydrochloric acid used to neutralise exactly

25 cm3

of sodium hydroxide solution?

14

(iii) Based on your answer in d(ii), determine the concentration of sodium hydroxide solution.

(iv) If a weak acid such as ethanoic acid 0.1 mol dm-3

is used to replace hydrochloric acid solution for thetitration process, predict the volume of the ethanoic acid that can neutralise 25 cm

3of the same sodium

hydroxide solution.

……………………………………………………………………………………………………………

15 (a) The table below shows the data obtained by a student to investigate the relationship between theconcentration of acid with the pH value of hydrochloric acid. The standard concentration ofeach solution is 0.1 mol dm

3. The solution is then diluted to give solutions with different concentrations.

pH value for each solution is determined with a pH meter and the value recorded.

Concentration / mol dm-3

0.1 0.01 0.001 0.0001 0.00001pH value 1.0 2.0 3.0 4.0 5.0

(i)Based on the information above, complete the table below.Name of variables Action to be taken(i) Manipulated variable:

……………………………………..

……………………………………..

(i) The way to manipulate variable:

………………………………………..

………………………………………...

(ii) Responding variable:

……………………………………

……………………………………

(ii) What to observe in the responding variable:………………………………………..

………………………………………..………

(iii) Controlled variable:

……………………………………..

……………………………………..

(iii) The way to maintain the controlled variable:

………………………………………

………………………………………

[6 marks](ii) State the hypothesis of the experiment.

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

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

(b) Why hydrochloric acid solution with the same concentration with ethanoic acid solution has alower pH value?

………………………………………………………………………………………………………..

……………………………………………………………………………………………………….[3 marks]


15

16. An experiment is carried out to investigate the effect of temperature on the rate of reaction of sodiumthiosulphate solution 0.05 mol dm

-3with hydrochloric acid solution 1.0 mol dm

-3. Time for a certain

quantity of sulphur precipitated is recorded as in Table 1 below.

Temperature of sodium thiosulphate /oC

30 35 40 45 50

Time for a certain quantity of sulphurprecipitated / s

55 48 42 37 33

1 / s-1

time

Table 1

(a) Based on the information above, complete the table below.

Name of variables Action to be taken(i) Manipulated variable:

……………………………………..

……………………………………..

(i) The way to manipulate variable:

………………………………………..

………………………………………...

(ii) Responding variable:

……………………………………

……………………………………

(ii) What to observe in the responding variable:………………………………………..

………………………………………..

(iii) Controlled variable:

……………………………………..

……………………………………..

(iii) The way to maintain the controlled variable:

………………………………………

………………………………………

[6 marks]

(b) State the hypothesis for this experiment.

……………………………………………………………………………………………………………

……………………………………………………………………………………………………………[3 marks]

1(c) Complete Table 1 for the values of —

time[3 marks]

1(d) Draw the graph of temperature against — on a graph paper.

time[3 marks]

(e) From the graph at (c), predict the time taken for a certain quantity of sulphur precipitates if theconcentration of sodium thiosulphate used is 0.01 mol dm

-3.

…………………………………………………………………………………………………………………[3 marks]


16

17 The figure below shows the experiment to determine the heat of combustion of ethanol. 200 cm3

of water isused in this experiment.

Beginning of Experiment End of Experiment

Initial temperature of water: ..................oC Final temperature of water: ....................

oC

Change in temperature: .......................oC

Initial mass of spirit lamp and ethanol: ........... g Final mass of spirit lamp and ethanol: ............ g

Mass of ethanol used: ......................... g

(a) Write the initial and final temperature of water and the initial and final mass of the spirit lamp withethanol in the diagram.

[3 marks](b) Construct a table that can be used to record the data from the experiment for temperature.

[3 marks]

(c) (i) Calculate the energy change in this experiment.[Given: Energy change = mc, specific heat capacity of water, c = 4.2 Jg

-1oC]

[3 marks]

60

65

55

20

25

15

217.5218.5


17

(ii) Calculate the number of moles of ethanol burnt in this experiment.[Molar mass of ethanol = 46 gmol

-1]

[3 marks]

(iii) Calculate the heat of combustion of ethanol in this experiment.

[3 marks](d) The table below shows the heat of combustion of three alcohols.

Name of alcohol Molecular formula Heat of combustion/k mol-1

Methanol CH3OH 725Ethanol C2H5OH 1376Propanol C3H7OH 2015

(i) Based on the table above, state the hypothesis for this experiment.

………………………………………………………………………………………..............................................[3 marks]

(ii) If ethanol is replaced with methanol for the experiment above, with the same amount of energychange, predict the mass of methanol burnt.[Given the molecular mass of CH3OH: 32 g mol

-1]

……...………………………………………………………………………………...............................................[3 marks]


18

Sample answer

1 (a) X waterY [organic solvent], example : benzene/ toluene / tetrachloromethane

(b) (i) HCl in solvent X / water(ii) The presence of X/ water will ionize HCl molecules to produce hydrogen ion / H

+

(c) (i) Carbon dioxide(ii) Passed the gas through the lime water, the lime water turn chalky(iii) 2H

++ CO3

2-CO2 + H2O

(d) In solvent X / water, hydrogen chloride molecules ionize to produce free moving hydrogen andchloride ions / H

+and Cl

-

In solvent Y / [tetracloromethane] hydrogen chloride remains in the form of molecules / do not ionize

(e) Number of mol of HCl = MV/1000

= 0.5 x 100 = 0.051000

Mass of HCl = number of mol x molar mass of HCl= 0.05 x 36.5 = 1.825 g

2 (a) (i) neutralization(ii) Sodium chloride

(b) Pink to colourless

(c) HCl + NaOH → NaCl + H2O

(d) (i) Number of mole of NaOH = 25 x 1 = 0.025 mol1000

Number of mole of HCl = 0.025 mol

0.025 = 1 x V1000

Volume of hydrochloric acid = 25 cm3

(ii) 12.5 cm3

Sulphuric acid is diprotic acid, hydrochloric acid is monoprotic acid.The concentration/number of hydrogen ions is the same

(e) Number of mole of NaCl = 0.025 molMass of NaCl = 0.025 x ( 23 + 35.5)

= 1,46 g(f) As a preservative

3(a) (i) Copper(II) oxide 1(ii) Heat strongly 1(iii) Passed the gas through the lime water , the lime water turns chalky 1

1 + 1Copper(II) carbonate

Heat
Lime water


19

(b)(i) All hydrochloric acid has reacted 1(ii) CuO + 2HCl CuCl2 + CO2 + H2O 1+1

(c) Heat the solution until saturated, cool the solution , filter and dry with filter paper 1Total 9

4(a) (i) nitric acid (dilute) 1(ii) PbO + HNO3 Pb(NO3)2 + H2O 1

(b) (i) Nitrogen dioxide 1(ii) 2Pb(NO3)2 2PbO + 4NO2 + O2 1

(c) (i) Precipitation reaction 1

(ii) Pb2+

+ 2Cl-

PbCl2 1

(ii) Filter, rinse with distill water 1

(d) White precipitate 1Dissolve in excess of sodium hydroxide solution 1

5.(a) lead(II) iodide 1(b) precipitation reaction. 1(c) 5 cm 1(d) 5 cm

31

(e) (i) the number of mole of sodium iodide= 1 x 10.0 // 0.01 mol 1

1000(ii the number of mole of lead(II) nitrate

= 1 x 5 // 0.005 mol 11000

(f) Pb2+

+ 2I- PbI2 1

(g)

1

2.5 5

(h) White precipitate 1

Dissolve in excess of sodium hydroxide solution 1

6 a) 2H2O2 → 2H2O + O2 1

b) Graph: X axis and Y axis are labelled with unit.t 1 Appropriate scale and consistence. 1 All points are plotted correctly 1 Smooth curve 1

c) i)060

029

= 0.483 cm

3s

-11

ii) Tangen at the curve is shown. 1(accept 0.2 – 0.3) cm

3s

-11

5


20

d) Number of mole of O2 =24000

36= 0.0015 mol

1 mol O2 : 2 mol H2O2

0.0015 mol O2 : 2(0.0015) mol H2O2 1

= 0.003

Concentration of H2O2 = 0.003 x25

1000= 0.12 mol dm

-31

e) Catalyst/manganese(IV) oxide lowers the activation energy of hydrogen peroxide molecule

The frequency of effective collision between hydrogen peroxide molecules increases

7 (a) Heat is released when 1 mol of copper is displaced from copper(II) sulphate solution by zinc

(b) Blue colour of copper(II) sulphate solution becomes colourless // brown solid is deposited //zinc dissolves/ the polystyrene cup becomes hot

1

(c) (i) Heat released = 50 x 4.2 x 5.2 J / 1092 J

Number of mole of copper(II) sulphate = 0.1 x 50 / 0.005 mol 11000

(ii) Heat of displacement = 10920.005 1

= - 218400 J mol-1

// 218.4 kJ mol-1

1[negative sign, correct answer with unit]

(d) Zinc + copper(II) sulphate

Zink sulphate + copper

1. The position and name/formulae for the reactants and products are correct 12 Label for the energy axis and arrow for the two levels are shown. 1

(e) lower/smaller 1The total surface area exposed to the air is larger 1Heat is lost to the environment 1

Energy


21

Essay Section B

8(a) - Glacial ethanoic acid only consist of molecules 1

- There are no free moving ions 1- In aqueous solution, ethanoic acid ionise to form free moving ions 1- CH3COOH

CH3COO

-+ H

+1

- H+

ions and CH3COO-ions which are free to move can coduct electric current 1

(b) - Hydrochloric acid is a strong acid whereas ethanoic acid is a weak acid 1- Ethanoic acid ionise partially in water to produce a low concentration of hydrogen ions. 1- Hydrochloric acid ionise completely in water to produce a high concentration of hydrogen ions. 1- The concentration of hydrogen ions in hydrochloric acid is higher than that in ethanoic acid. 1- Thus, hydrochloric acid has lower value of pH compared to ethanoic acid 1

(c) (i) - Reaction between acid and alkali 1- Reaction between acid and metal oxide 1- Reaction between acid and reactive metal 1- Reaction between acid andmetal carbonate( Any 3 from above)

(ii) - 50 cm3

of 1 moldm-3

hydrochloric acid is measured using a measuring cylinder and poured into abeaker and 1

- heated slowly. 1- Using spatula, zinc carbonate 1- is added bit by bit by stirring the hydrochloric acid until some of it no longer dissolves. 1- The hot solution is filtered. 1- The filtrate is poured into an evaporating dish. 1- The salt solution is gently heated until saturated. 1- The hot saturated salt solution is allowed to cool for crystals to form. 1- The crystals formed are filtered out, washed with a little cold distilled water

and dried between sheets of filter paper. 1Max 7

9 (a) Collisions which achieve activation energy and with correct orientation. 1 + 1

(b) (i) Mg + 2H+ Mg

2++ H2 1

Comparing experiment II and experiment I

Ethanoic acid is a strong acid, whereas hydrochloric acid is a strong acid //Ethanoic acid ionises partially, whereas hydrochloric acid ionises completely in water.

1Concentration of H

+ions in hydrochloric acid is high. 1

The frequency of collision between H+

ions and magnesium is high. 1


22

Comparing experiment II and experiment III

Sulphuric acid is a diprotic acid, whereas hydrochloric acid is a monoprotic acid //1 mole of sulphuric acid ionises to produce 2 mole of hydrogen ions,whereas 1 mole of hydrochloric acid ionises to produce 1 mole of hydrogen ions. 1

Concentration of H+

ions in sulphuric acid is higher than that in hydrochloric acid. 1

Comparing experiment II and experiment IV

Copper(II) sulphate solution is a catalyst 1It lower down the activation energy 1The number of effective collision increases. 1

(ii) The time taken becomes shorter. 1

When the temperature increases, the kinetic energy of H+

ions increases /H

+ions move faster. 1

The frequency of collision between H+

ions and magnesium atom increases //The number of effective collision increases. 1

(c) (i) The decaying and decomposition of food is a chemical reaction caused by the action ofmicroorganisms (bacteria or fungi) 1The temperature in refrigerator is lower than the temperature in kitchen cabinet. 1Low temperature slow down the activities of microorganisms. 1

(ii) Meat in small pieces has larger total surface area, whereas 1Meat in big chunks has smaller total surface area. 1Heat can be absorbed faster. 1

10 a) Mg + H2SO4 → MgSO4 + H2 1Esperiment I:

Number of mole of H2SO4 =1000

110= 0.01 1

1 mole of H2SO4 produce 1 mole of H2

0.01 mole of H2SO4 produce 0.01 mole of H2 1

Volume of hydrogen gas = 0.01 x 24000= 240 cm

31

Eksperimen II:

Number of mole of H2SO4 =1000

210= 0.02 1

Volume of hydrogen gas = 0.02 x 24000= 480 cm

31


23

b)

3

c) Average rate of reaction:

Experiment I =60

240= 4 cm

3s

-11

Experiment II =30

480= 16 cm

3s

-11

Experiment III =10

480= 48 cm

3s

-11

d) Comparing experiment I and experiment II:1. The concentration of sulphuric acid in experiment II is higher than that in experiment I . 1

//The number of reacting particles/ H+

ions per unit volume of acid increases.2. The frequency of collision between H

+ions and magnesium atom increases. 1

3. The frequency of effective collision increases. 14. Thus, the rate of reaction of experiment II is higher than the rate of reaction of experiment I. 1

Comparing experiment II and experiment III:1. The total surface area of magnesium in experiment III is larger than that in experiment II. 12. The frequency of collision between H

+ions and magnesium atom increases. 1

3. The frequency of effective collision increases. 14. Thus, the rate of reaction of experiment III is higher than the rate of reaction of experiment II. 1

Volume ofhydrogen gas/ cm

3

Time / s

II

III

480

240

I


24

11(a) [Able to name a soluble salt and insoluble salt]

Example:

1 Soluble salt: copper(II) sulphate 1

2 Insoluble salt: barium sulphate 1

3 H2SO4 + CuO CuSO4 + H2O //H2SO4 + CuCO3 CuSO4 + H2O + CO2 1

4 BaCl2 + Na2SO4 BaSO4 + 2NaCl 1

[Notes] :- All nitrate salts are soluble.

- All potassium, sodium and ammonium salts are soluble.

- All sulphate salts are soluble except PbSO4, CaSO4 and BaSO4.

- All chloride salts are soluble except PbCl2, AgCl and HgCl2.

- All carbonate salts are insoluble except K2CO3, Na2CO3 and (NH4)2CO3

(b) [Able to give appropriate chemical test]

1 Zinc nitrate crystals are dissolved in distilled water and 1the solution is divided into two portions in two test tubes. 1

2 For the first portion, ammonia solution is added drop by drop untill in excess. 13 A white precipitate is formed and insoluble in excess ammonia solution. 14 For the second portion, dilute sulphuric acid is added follow by iron(II) sulphate solution.

The mixture is shaken well. 15 Then, concentrated sulphuric acid is added carefully down the side of the test tube. 16 A ”brown ring” is formed.

(c) [Able to describe the procedure to prepare magnesium nitrate salt ]

1 Magnesium sulphate solution is added to sodium carbonate solution in a beaker. 12 The mixture is shaken well/ stirred and a white solid, MgCO3 is formed. 13 The white precipitate is filtered out and rinsed with distilled water. 14 The white precipitate is added to the nitric acid in a beaker until in excess/ some of it no

longer dissolves. 15 The excess white precipitate is filter out. 16 The filtrate is poured into an evaporating dish. 17 The salt solution is gently heated until saturated. 18 The hot saturated salt solution is allowed to cool for crystals to form. 19 The crystals formed are filtered out, washed with a little cold distilled water. 1

and dried between sheets of filter paper.Max 8

10 Chemical equations:

MgSO4 + Na2CO3 MgCO3 + Na2SO4 1

MgCO3 + 2HNO3 Mg(NO3)2 + H2O + CO2 1


25

12 a) In a pressure cooker, the high pressure raises the boiling pointof water to a temperature above 100

0C. 1

A high temperature, food can be cooked faster. 1

b) Example:Industrial process CatalystAmmonia (Haber Process) Iron powderSulphuric acid (Contact process) Vanadium(V) oxideNitric acid (Ostwald process) PlatinumMargarine (Hydrogenation) Nickel

(Any 2 from above)c) Apparatus 1

Material 1Diagram 2Procedure 7Table 2Discussion 3

Materials:Hydrochloric acid, 0.2 moldm

-3, large marble chip, small crushed marble chips, and water.

Apparatus:Measuring cylinder, conical flask, stopper with delivery tube, basin, burette, electronic balance, stopwatch

Diagram:

Procedure:1. A burette filled with water is inverted over water in a basin and clamped vertically using a retort stand.2. The initial burette reading is recorded.3. 40 cm

3of hydrochloric acid, HCl is measured using a measuring cylinder and poured into a conical flask.

4. 2 g of large marble chips is weighed and added to the acid in the conical flask.5. The conical flask is closed immediately with a stopper fitted with a delivery tube. At the same time, a

stopwatch is started. The conical flask is shaken gently.6. The volume of carbon dioxide gas released is collected in the burette.7. The burette reading is recorded at regular intervals of ½-minute(30 seconds) until no more gas is liberatedSteps 1 to 8 are repeated using 2 g of small crushed marble chips.

Result:Experiment 1 : Using large marble chipsTime(min) 0Burette reading (cm3) 50.00Volume of CO2 (cm3)

Experiment 2 : Using small crushed marble chipsTime(min) 0Burette reading (cm3) 50.00Volume of CO2 (cm3)

[2 marks]

Hydrochloricacid

Marble chipWater


26

Discussion:

1. [Sketch the graph of volume of carbon dioxide gas against time for the both experiment on the same axis]

[2 marks]

2. By comparison, the initial gradient of graph 2 is higher than the initial gradient of graph 1.Therefore, small size of marble chips increases the rate of reaction. [1 mark]

13 (a) The heat of neutralisation is the heat produced whenone mole of water is formed from the reaction between an acid and alkali./ 1 mole of H

+ion react with 1 mole of OH

-ion to form one mole of water. 1

(b) Comparing the heat of reaction of Reaction I and Reaction IINaOH and KOH are strong alkalis, whereasHCl and HNO3 are strong acids. 1

Both reactions involved combination of 1 mole of hydrogen ions and1 mole of hydroxide ions to produce 1 mole of molecule water. 1

Comparing the heat of reaction of Reaction III and Reaction I

Sulphuric acid is a strong diprotic acid. 1The reaction between sulphuric acid and sodium hydroxide involved2 mole of hydrogen ions and 2 mole of hydroxide ions to produce2 mole of molecule waters. 1

Comparing the heat of reaction of Reaction IV and Reaction IIn reaction IV, ethanoic acid is a weak acid// ionises partially in waterTo produce hydrogen ions of low concentration. 1

Some of the heat given out is used to dissociate the molecule ofethanoic acid completely in water. 1

Heat of neutralisation of reaction III is 57kJmol-1

and not 14kJmol-1

Because the heat of neutralisation is the heat produced whenone mole of water is formed. 1Thus, 114 kJ ÷ 2 mol = - 57kJmol

-1

(b) 50 cm3

of 2 moldm-3

sodium hydroxide solution is measured using a measuring cylinderand poured into a plastic cup. 1The initial temperature of the solution is measured after a few minutes. 150 cm

3of 2 moldm

-3hydrochloric acid is measured using another measuring cylinder

and poured into a plastic cup. 1The initial temperature of the solution is measured after a few minutes. 1The hydrochloric acid is then poured quickly and carefully into the sodiumhydroide solution. 1The mixture is stirred using a thermometer and the highest temperature reachedis recorded. 1

Max 5

Volume ofCO2 gas

(cm3)

Time (min)


27

Results:Initial temperature of sodium hydroxide solution = T1

0C.

Initial temperature of hydrochloric acid = T20C

Highest temperature = T30C 1

Calculation:Average temperature of acid and alkali = T1 + T2

2= Tx

0C 1

Increase in temperature = (T3-Tx) = Ø0C 1

Heat released in the reaction = (50 +50) ( C ) Ø= P Joule 1

Number of mole of sodium hydroxide and hydrochloric acid= 50 x 2

1000= 0.1 mol 1

0.1 mole of hydrochloric acid reacts with 0.1 mole of sodium hydroxideto release P joule of heat.

0.2 Thus , 1 mole of hydrochloric acid reacts with 1 mole of sodium hydroxideto release 1 X P joule haba = Q joule 1

0.1

Heat of neutralisation, ΔH =1000

QkJmol

-11

Paper 3

14(a) The higher the concentration of the hydrochloric acid, the lower the pH value. 3(b) The concentration of the hydrogen ions, H

+in the acid decreases 3

(c) (i)

Titration Number 1 2 3Final reading 24.90 49.50 25.70Initial reading 0.10 24.90 1.00

Volume of hydrochloric acid used 24.80 24.60 24.70

3

(ii)[Steps for calculation]24.70 cm

3 3

(iii)[Steps for calculation]0.0988 mol/dm

3 3

(iv) Volume is bigger than 24.70 cm3 3

18

15 (a) (i)

Manipulated variable:

Concentration of hydrochloricacid

Way to manipulate:

Dilute the acid to different concentrations: 0.1mol dm

-3, 0.01 mol dm

-3, 0.001 mol dm

-3, 0.0001

mol dm-3

, dan 0.00001 mol dm-3

Responding variablepH value

What to observe:The lower the concentration of hydrochloric acid,the bigger the pH value.

Fixed variable:Type of acid

Way to fix the variableUse the same type of acid in each experiment


28

[6 marks](a) (ii) [ To make hypothesis]

Score Explanation3 The higher the concentration of acid, the lower the pH value.

(b) [Interpreting data]

Score Explanation3 Hydrochloric acid is a strong acid, that will ionise completely in water to give

high concentration of H+

ions.Ethanoic acid is a weak acid, ionise partially in water to low concentration of H

+

ions.

Explanation Score

16(a) Suggested answerManipulated variable:Temperature of sodiumthiosulphate solution.

Heat the solution to differenttemperatures

Responding variable:Rate of reaction //Time for acertain quantity ofprecipitate formed

Take the time taken: Time decreaseswith increased temperature

Fixed variable:Volume and concentrationof hydrochloric acid//Volume and concentrationof sodium thiosulphate

Use the same volume andconcentration of sulphuric acid //sodium thiosulphate solution for eachexperiment.

6

3(b) [Able to relate the manipulated variable and the responding variable]Answer:The higher the temperature of the sodium thiosulpate solution, the higher therate of reaction // The higher the temperature of the sodium thiosulpate solution,the shorter the time taken for a certain quantity of sulphur precipitate formed

3

3(c)(i) Values of 1/time: 1 0.018, 0.021, 0.024, 0.027, 0.030 33(c)(ii) Able to draw graph with the following characteristics:

x-axis is labelled with 1/time and with unit second-1

y-axis is labelled with temperature and with unitoC

Consistent scale and size of graph at least 1/3 the size of graph paper.

Correct tranfer of plots

Graph passed through / near the origin and smooth

3

3(d) Able to determine the time from the graph.1/t = 0.005t = 200 s

3


29

Explanation Score17(a)

Initial temperature: 25oC

Final temperature: 65oC

Change in temperature: 20oC

Initial mass of spirit lamp + ethanol: 218.5 gFinal mass of spirit lamp + ethanol : 217.5 gMaas of ethanol used: 1.0 g

3

(b)Initial temperature /

oC 25

Final temperature /oC 65

Change in temperature/oC 20

3

(c)(i) Energy change = 200 x 4.2 x 20= 16800 J

3

(ii) No. of moles of ethanol burnt = 1/46= 0.02

3

(iii) Heat of combustion of ethanol = - 168000.02

= - 840000 J mol-1

(d) The bigger the number of carbon atoms per molecule ofalcohol, the bigger the value of heat of combustion.

3

(e) 0.736 g 3

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KIMIA SET 3 Perfect Score