June 1999 Paper 2

Centre Number

Candidate Number

Candidate Name

UNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATE General Certificate of Education Ordinary Level

5070/2

CHEMISTRY PAPER 2 Theory Friday

18 JUNE 1999

Morning

1 hour 30 minutes

Additional materials: Answer paper Electronic calculator and/or Mathematical tables

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 on any 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 and continue 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 question or part question. Mathematical tables are available. You may use a calculator. A copy of the Periodic Table is printed on page 16.

FOR EXAMINER’S USE Section A B7 B8 B9 B10 TOTAL

This question paper consists of 13 printed pages and 3 lined pages. SB ( SC) QF92363/3 © UCLES 1999

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2

For Examiner’s Use

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 electrolysed using carbon electrodes, ..............................................................................................................................................[1] (d) changes acidified potassium dichromate(VI) from orange to green. ..............................................................................................................................................[1]

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For Examiner’s Use

3 A2 The table gives information about some substances.

substance

melting point

boiling point

electrical conductivity

solubility in water

copper

high

very high

good

insoluble

magnesium oxide

very high

very high

poor

insoluble

A

high

high

poor

soluble

B

low

low

poor

insoluble

C

very high

very high

good

insoluble

D

high

high

poor

insoluble

E

low

low

poor

very soluble

(a) Explain, in terms of its structure, how copper conducts electricity. .......................................................................................................................................... ......................................................................................................................................[2] (b) (i) (ii)

Which one of the substances could be methane, CH4? ........................................... 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, NaCl? ..................................[1]

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4 (d) (i)

(ii)

Magnesium oxide has the same lattice structure as sodium chloride. Draw the lattice structure of magnesium oxide.

Magnesium oxide has a very high melting point. Give one use of magnesium oxide that depends on this property. ...............................................................................................................................[3]

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For Examiner’s Use

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For Examiner’s Use

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 are absorbed.

pH ion 4

5

6

7

8

Al 3+

✔

✔

✔

Ca2+

✔

✔

✔

✔

✔

Fe3+

✔

✔

✔ ✔

✔

✔

✔

✔

✔

NO3–

✔

✔

✔

PO43–

✔

✔

✔

Zn2+

✔

✔

✔

K+ Mg2+

✔

✔

9

10

✔

✔

✔

✔

✔ = 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 acidic rainfall. ................................................................................................................................... ...............................................................................................................................[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] 5070/2 S99 [Turn over

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For Examiner’s Use

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

H

G

H

H

H

H

C

C

C

C

H

H

H

H

H

H

H

H

H

H

C

C

C

C

H

H

H

H

H

I

H H

O

C

OH

H

C OH

H

H

H

H

C

C

C

H

H

H

O C OH

J H H

C H

(a) (i)

O C O

H

H

C

C

H

H

H

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 but different structures? ................................................................................................................................... [2]

(b) Compound F has the molecular formula C4H10. Draw the structure of another compound with this molecular formula.

[1]

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For Examiner’s Use

(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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8 A5 The table gives some properties of the elements in Group VII. The properties for astatine are missing from the table.

atomic symbol

electronic structure

melting point/°C

boiling point/°C

atomic radius/pm

fluorine

F

2.7

–220

–188

64

chlorine

Cl

2.8.7

[–101]

–35

99

bromine

Br

2.8.18.7

–7

59

114

iodine

I

2.8.18.18.7

113

183

133

astatine

At

element

(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 chlorine is added to an aqueous metal halide.

aqueous halide

observation

potassium bromide

colourless solution turns orange

names of products

potassium iodide (ii)

Give the ionic equation for one of the above reactions. ...............................................................................................................................[4]

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For Examiner’s Use

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For Examiner’s Use

(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 oxidation has taken place.

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

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

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10 A6 Potassium superoxide, KO2, is an ionic solid. It can be used in spacecraft to supply oxygen according to the following equation. 4KO2(s) + 2H2O(l) → 4KOH(s) + 3O2(g) The potassium hydroxide formed removes carbon dioxide. (a) Show that 1.0 g of potassium superoxide will supply about 0.25 dm3 of oxygen at room temperature and pressure.

[3] (b) (i)

Name the compound formed when carbon dioxide reacts with solid potassium hydroxide. ...................................................................................................................................

(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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For Examiner’s Use

11 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 C16H34. Construct an equation to illustrate the cracking of C16H34, to make ethene and another hydrocarbon 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 treated before 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, Fe2+, and iron(III) ions, Fe3+. 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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12 B9 In the Contact process for the manufacture of sulphuric acid, sulphur dioxide is converted into sulphur trioxide. 2SO3(g) ∆H = –98 kJ mol–1

2SO2(g) + O2(g)

(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 dilute sulphuric 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)

temperature of electrolyte/°C

current used/kA

time/days

mass of aluminium made/tonnes

1000

60

1

1

1000

120

1

2

1250

120

1

2

1000

60

2

2

Use the information in the table to deduce which factor does not affect the mass of aluminium made.

(ii)

Predict the mass of aluminium made in 2 days if a current of 180 kA is passed through the 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] 5070/2 S99

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Magnesium

Sodium

Calcium

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Strontium

45

Key

b

X

a

*

89

227

Actinium

Ac

b = proton (atomic) number

X = atomic symbol

a = relative atomic mass

†

72

Hafnium

Lanthanum

57

178

Hf

40

Zirconium

Zr

91

Titanium

139

Yttrium

Y

89

22

48

Ti

La

39

21

Scandium

Sc

*58-71 Lanthanoid series †90-103 Actinoid series

88

Radium

87

Francium

226

Ra

56

Barium

Caesium

Fr

55

137

Ba

133

Cs

38

Rubidium

37

88

Sr

85

Rb

20

Potassium

19

40

Ca

39

12

24

Mg

23

Na

Beryllium

4

Lithium

K

11

3

9

Be

7

II

Li

I

93

Ta

181

Niobium

Nb

90

58

73

52

96

Mo

W

184

Protactinium

Thorium

55

Tc 186

Re

144

Nd

92

60

Uranium

U

238

Neodymium

75

Rhenium

43

Technetium

25

Manganese

Mn 27

59

28

59

29

64

30

65

5

Ru

101

Iron

190

Pm

Osmium

Os

Np 93

Neptunium

61

Promethium

76

44

Ruthenium

26

56

Fe

Sm

150

Iridium

Pu 94

Plutonium

62

152

Eu

Am 95

Americium

63

Europium

78

Platinum

195

Pt

Ir

46

Palladium

Pd

106

Nickel

Ni

192

Samarium

77

45

Rhodium

Rh

103

Cobalt

Co

Gd

157

Gold

Au

197

Silver

96

64

Curium

Cm

Gadolinium

79

47

Ag

108

Copper

Cu

201

Bk

Terbium

Tb

159

Mercury

Hg

97

Berkelium

65

80

48

Cadmium

Cd

112

Zinc

Zn

11

6

Dy

162

Thallium

Tl

204

Indium

Cf 98

Californium

66

Es

Holmium

Ho

165

Lead

Pb

207

Tin

99

Einsteinium

67

82

50

119

Sn

115

32

Germanium

Ge

73

Silicon

In

Gallium

Dysprosium

81

49

31

70

Ga

14

28

Si

Carbon

27

Aluminium

13

12

C

Al

Boron

B 7

14

75

Sb

122

Arsenic

As

Bi

209

Fermium

Fm

Erbium

Er

167

Bismuth

100

68

83

51

Antimony

33

15

Phosphorus

P

31

Nitrogen

N 8

Se

79

Sulphur

S

32

Oxygen

Po

169

Md

Thulium

Tm

101

Mendelevium

69

84

Polonium

52

Tellurium

Te

128

Selenium

34

16

16

O 9

Yb

173

Astatine

At

Iodine

I

127

Bromine

Br

80

Chlorine

No 102

Nobelium

70

Ytterbium

85

53

35

17

Cl

35.5

Fluorine

F

19

Lr

Lutetium

Lu

175

Radon

Rn

Xenon

Xe

131

Krypton

Kr

84

Argon

Ar

40

Neon

103

Lawrencium

71

86

54

36

18

10

Ne

20

Helium

2

0

Hydrogen

VII

4

VI

He

V

1

IV

H

III

The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).

91

Pa

Th

232

Praseodymium

Cerium

59

141

Pr

140

74

Tungsten

42

Molybdenum

24

Chromium

Cr

Ce

Tantalum

41

23

Vanadium

V

51

1

Group

DATA SHEET The Periodic Table of the Elements

16