June 1999 Paper 2

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TIME 1 hour 30 minutes

INSTRUCTIONS TO CANDIDATES

Write your name, Centre number and candidate number in the spaces at the top of this page and onany separate answer paper used.

Section A

Answer all questions.

Write your answers in the spaces provided on the question paper.Section B

Answer any three questions.

Where lined pages are provided at the end of the question paper, write your answers on these andcontinue on separate answer paper.

At the end of the examination, fasten any separate answer paper used securely to the question paper.

INFORMATION FOR CANDIDATES

The number of marks is given in brackets [ ] at the end of each questionor part question.

Mathematical tables are available.

You may use a calculator.

A copy of the Periodic Table is printed on page 16.

UNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATEGeneral Certificate of Education Ordinary Level

CHEMISTRY 5070/2PAPER 2 Theory

Friday 18 JUNE 1999 Morning 1 hour 30 minutes

Additional materials:Answer paperElectronic calculator and/or Mathematical tables

This question paper consists of 13 printed pages and 3 lined pages.SB ( SC) QF92363/3

UCLES 1999 [Turn over

CandidateCentre Number Number

Candidate Name

FOR EXAMINERS USE

Section A

B7

B8

B9

B10

TOTAL

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Section A

Answer all the questions in this section in the spaces provided.

The total mark for this section is 45.

A1 Choose from the following gases to answer the questions below.

ammonia carbon dioxide carbon monoxide chlorine

hydrogen nitrogen oxygen sulphur dioxide

Each gas can be used once, more than once, or not at all.

Name a gas which

(a) is used to bleach wood pulp,

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

(b) is used in the manufacture of margarine,

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

(c) is formed at the cathode when concentrated aqueous sodium chloride is electrolysedusing carbon electrodes,

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

(d) changes acidified potassium dichromate( VI ) from orange to green.

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

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A2 The table gives information about some substances.

(a) Explain, in terms of its structure, how copper conducts electricity.

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

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

(b) (i) Which one of the substances could be methane, CH 4? ...........................................

(ii) Draw a dot and cross diagram to show all the electrons in a methane molecule.

[3]

(c) Which one of the substances could be sodium chloride, NaC l? ..................................[1]

substance

copper high very high good insoluble

very high very high poor insoluble

high high poor soluble

low low poor insoluble

very high very high good insoluble

high high poor insoluble

low low poor very soluble

magnesium oxide

A

B

C

D

E

meltingpoint

boilingpoint

electricalconductivity

solubility inwater

3

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(d) (i) Magnesium oxide has the same lattice structure as sodium chloride.Draw the lattice structure of magnesium oxide.

(ii) Magnesium oxide has a very high melting point. Give one use of magnesium oxidethat depends on this property.

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

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A3 Fertilisers provide essential elements for plant growth.

(a) Name the three main essential elements provided by fertilisers.

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

(b) Plants absorb ions through their roots. The table shows the pH at which the ions areabsorbed.

= ion is absorbed.(i) At what pH does a plant absorb all the ions listed in the table?

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

(ii) Which two ions are not absorbed in neutral conditions?

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

(iii) Aluminium ions are poisonous to plants.

Suggest why aluminium poisoning is more likely to occur in regions with acidicrainfall.

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

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

(c) (i) Give one reason why it is important to control the pH of soil.

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

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

(ii) Name a compound that is used to increase the pH of acidic soil.

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

ionpH

4 5 6 7 8 9 10

Al 3+

Ca 2+

Fe 3+

K+

Mg2+

NO 3

PO 43

Zn 2+

5


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A4 Diagrams F to J show the structure of some organic compounds.

(a) (i) Give the letters of the two compounds that have the same molecular formula.

compounds ..............................................and ..........................................................

(ii) Which term describes compounds that have the same molecular formula butdifferent structures?

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

(b) Compound F has the molecular formula C 4H10 .

Draw the structure of another compound with this molecular formula.

[1]

H

H

H HC

H

H

C

H

H

C

H

H

O C

H

H

C H

H

H

C

F

H

H

H OHC

H

H

C

H

H

C

H

H

C

G

H

H

H C

O

OH

C

O

OH

C

H

H

H

H C

O

C

J

H

H

H C

H

H

C

H

H

C

I

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(c) Give the letters of two compounds that react together to form an ester.

compounds .....................................................and ......................................................[1]

(d) Give the letter of the compound formed by the oxidation of ethanol.

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

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A5 The table gives some properties of the elements in Group VII. The properties for astatine aremissing from the table.

(a) (i) Which halogen is a liquid at room temperature and pressure?

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

(ii) How many electrons does one atom of astatine have in its outer shell?

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

(iii) Predict the atomic radius of astatine.

..............................................................................................................................pm

(iv) Predict the state and colour of astatine at room temperature and pressure.state ..........................................................................................................................

colour ........................................................................................................................

(v) Predict the molecular formula for astatine.

...............................................................................................................................[6]

(b) (i) Complete the following table that describes what happens when aqueous chlorineis added to an aqueous metal halide.

(ii) Give the ionic equation for one of the above reactions.

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

element

fluorine F

chlorine C l

Br

I

At

bromine

iodine

astatine

atomicsymbol

electronicstructure

2.7 220 188 64

[101 ] 35 99

7 59 114

113 183 133

2.8.7

2.8.18.7

2.8.18.18.7

meltingpoint/C

boilingpoint/C

atomicradius/pm

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aqueoushalide

potassiumbromide

potassiumiodide

observation

colourless solution turnsorange

names of products

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(c) Chlorine will oxidise aqueous iron( II ) chloride to form aqueous iron( III ) chloride.

(i) Explain why this is a redox reaction.

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

(ii) Describe how aqueous sodium hydroxide can be used to show that the oxidationhas taken place.

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

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

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A6 Potassium superoxide, KO 2, is an ionic solid. It can be used in spacecraft to supply oxygenaccording to the following equation.

4KO2(s) + 2H 2O(l) 4KOH(s) + 3O 2(g)

The potassium hydroxide formed removes carbon dioxide.

(a) Show that 1.0 g of potassium superoxide will supply about 0.25 dm 3 of oxygen at roomtemperature and pressure.

[3]

(b) (i) Name the compound formed when carbon dioxide reacts with solid potassiumhydroxide.

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

(ii) Give the equation for the formation of this compound.

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

(c) Supplies of oxygen in hospitals are stored in cylinders.

(i) State one other use for oxygen.

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

(ii) Describe briefly how oxygen is obtained from air.

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

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

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

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Section B

Answer three questions from this section. The total mark for this section is 30.

Write your answers on the lined pages that follow.

B7 Ethene is an unsaturated hydrocarbon.

(a) What is meant by the term unsaturated ? [1]

(b) Ethene is made by the cracking of long chain hydrocarbon molecules such as C 16 H34 .

Construct an equation to illustrate the cracking of C 16 H34 , to make ethene and anotherhydrocarbon as the only products. [1]

(c) Ethene is bubbled through aqueous bromine to form 1,2-dibromoethane.

What would you observe during the reaction? [2]

(d) Give the name of the product and the conditions needed for the reaction of ethene with water.[2]

(e) Calculate the volume of carbon dioxide, measured at room temperature and pressure,produced by the complete combustion of 1.40 g of ethene. [3]

(f) Ethene can be made into poly(ethene).

Draw the structure of poly(ethene). [1]

B8 (a) Under what conditions does water react with

(i) sodium,

(ii) magnesium?

In each case, name the products formed.[4]

(b) Water supplies are obtained from rivers, boreholes and reservoirs. The water must be treatedbefore use.

Describe and explain the two main processes in the purification of water supplies. [4]

(c) Water supplies that have passed through iron pipes contain iron( II ) ions, Fe 2+ , and iron( III )ions, Fe 3+ .

In the presence of air iron( II ) ions are slowly changed to iron( III ) ions.

Construct the equation for the reaction between iron( II ) ions, hydrogen ions, H +, and oxygen

to form iron(III

) ions and water. [2]

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B9 In the Contact process for the manufacture of sulphuric acid, sulphur dioxide is converted intosulphur trioxide.

2SO 2(g) + O 2(g) 2SO 3(g) H = 98 kJmol1

(a) This reaction reaches a dynamic equilibrium.

Explain what is meant by the term dynamic equilibrium . [2]

(b) A mixture of sulphur dioxide, oxygen and sulphur trioxide was allowed to reach equilibrium,then the temperature was raised.

Predict the effect of raising the temperature on

(i) the composition of the equilibrium mixture,

(ii) the rate of reaction.

Explain your answers. [4]

(c) Describe how you would prepare a pure dry sample of sodium sulphate starting with dilutesulphuric acid. [4]

B10 Aluminium is manufactured from aluminium oxide.

Aluminium oxide is dissolved in molten cryolite and this solution is electrolysed.

(a) Name the gas formed at the anode and describe a test to identify the gas. [2]

(b) Write equations for the reactions at the

(i) cathode,

(ii) anode.[2]

(c) The table shows how various factors affect the mass of aluminium made in a factory.

(i) Use the information in the table to deduce which factor does not affect the mass ofaluminium made.

(ii) Predict the mass of aluminium made in 2 days if a current of 180 kA is passed throughthe electrolyte at 1000 C.

[2](d) Iron is manufactured from haematite, an oxide of iron.

(i) Briefly describe the manufacture of iron from haematite.

(ii) Explain why aluminium is extracted by electrolysis whereas iron is not.[4]

1000 60 1 1

2

2

2

1

2

120

120

60

1000

1250

1000

temperature ofelectrolyte/C

1

current used/kA time/days mass of aluminiummade/tonnes

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G r o u p

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June 1999 Paper 2