June 2000 - 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 MAY/JUNE SESSION 2000

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. Write your answers on the 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.

FOR EXAMINER’S USE

A copy of the Periodic Table is printed on page 12. Section A B8 B9 B10 B11 TOTAL

This question paper consists of 12 printed pages. SB (DJ) QF06368/4 © UCLES 2000

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For Examiner’s Use

2 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 substances to answer the questions below. aluminium

ammonia

iron

lithium

magnesium oxide

potassium hydroxide

silicon

sulphur dioxide

Each substance can be used once, more than once, or not at all. Name a substance which (a) is an acidic gas, ......................................................................................................................................[1] (b) is a compound with a very high melting point and can be used in the lining of furnaces, ......................................................................................................................................[1] (c) is a metal with a high melting point and a high density, ......................................................................................................................................[1] (d) is a solid at room temperature and dissolves in water to form an alkaline solution, ......................................................................................................................................[1] (e) is an element which is soft with a low density. ......................................................................................................................................[1]

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3 A2 Two isotopes of carbon are carbon-12 and carbon-13. The proportion of these isotopes in ivory elephant tusks can be used to determine where in the world the tusks come from.

For Examiner’s Use

(a) What is the meaning of the term isotopes? .......................................................................................................................................... ......................................................................................................................................[1] (b) Complete the table about atoms of carbon-12 and carbon-13. isotope

symbol

carbon-12

12 6C

number of protons number of electrons number of neutrons per atom per atom per atom 6

6

6

carbon-13 [2] (c) Elephants eat plants that contain carbon-12 and carbon-13 combined in compounds such as carbohydrates. Carbohydrates in plants are formed from glucose that is made by the process of photosynthesis. Briefly describe, including a word equation, the process of photosynthesis. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3]

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For Examiner’s Use

4 A3 Alkenes are an homologous series of hydrocarbons. The table below shows the properties of some alkenes. alkene

melting point/°C

boiling point/°C

-169

-105

-185

-48

C4H8

-185

-6

pentene

C5H10

-165

30

hexene

C6H12

-140

64

ethene

molecular formula C2H4

propene

(a) Describe how alkenes are manufactured. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) Name the alkene with the molecular formula C4H8. ......................................................................................................................................[1] (c) What is the molecular formula of propene? ......................................................................................................................................[1] (d) Name an alkene that is a liquid at room temperature. ......................................................................................................................................[1]

(e) Draw a ‘dot and cross’ diagram to show the bonding in ethene. You need only draw the electrons in the outer shells of carbon and hydrogen.

[2] (f)

(i)

Write the equation for the reaction between ethene and steam. ...................................................................................................................................

(ii)

What name is given to this type of reaction? ...............................................................................................................................[2] 5070/2 S00

5 A4 (a) An excess of hydrochloric acid in the stomach causes indigestion. An indigestion tablet contains a mixture of calcium carbonate and magnesium hydroxide. Give the formulae of two salts formed when the tablets react with hydrochloric acid.

For Examiner’s Use

............................................................... and ...............................................................[2] (b) 3.0 dm3 of 0.10 mol/dm3 hydrochloric acid is spilled on a laboratory floor. The spilt acid is neutralised by 1.0 mol/dm3 aqueous sodium hydrogencarbonate. HCl(aq) + NaHCO3(aq) → NaCl (aq) + CO2(g) + H2O(l) Calculate the volume of aqueous sodium hydrogencarbonate needed to neutralise the hydrochloric acid.

[2] (c) Aqueous ammonia is spilled on a laboratory floor. Name a compound that will neutralise the ammonia. ......................................................................................................................................[1] (d) Some plants cannot grow in soils that are too acidic. Name a solid that is used to neutralise acidic soils. ......................................................................................................................................[1]

A5 Aqueous iron(II) ions react with acidified potassium manganate(VII) according to the equation below. 5Fe2+(aq) + 8H+(aq) + MnO4-(aq)

→ 5Fe3+(aq) + 4H2O(l) + Mn2+(aq)

(a) What is the reducing agent in this reaction? Explain your answer. .......................................................................................................................................... ......................................................................................................................................[2] (b) Describe briefly how aqueous potassium iodide can be used to test for an oxidising agent. .......................................................................................................................................... ......................................................................................................................................[1]

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6 A6 Many cars are fitted with air-bags which inflate in an accident. Air-bags contain the solid sodium azide, NaN3, which decomposes rapidly to form sodium and nitrogen. The nitrogen formed fills the air-bag. (a) Construct the equation, including state symbols, for the decomposition of sodium azide. ......................................................................................................................................[2] (b) In a crash, an air-bag fills with 72 dm3 of nitrogen at room temperature and pressure. What mass of sodium azide is needed to provide the nitrogen?

[3] (c) Sodium azide, NaN3, reacts with dilute hydrochloric acid to give sodium chloride and a compound A. Compound A contains 2.33 % hydrogen and 97.7% nitrogen by mass. (i)

What is the empirical formula for compound A?

(ii) Construct the equation for the reaction between sodium azide and dilute hydrochloric acid. ...............................................................................................................................[3]

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For Examiner’s Use

For Examiner’s Use

7 A7 Calcium carbonate reacts with dilute nitric acid to give carbon dioxide. The rate of reaction can be investigated by measuring the change in mass of a mixture of calcium carbonate and nitric acid over a period of time. As carbon dioxide escapes, the mixture loses mass. The graph below shows the results obtained when a 3.0 g lump of calcium carbonate was added to an excess of 1.0 mol/dm3 nitric acid.

mass of calcium carbonate and acid/g

0

10

20

time/minutes (a) Name the other products of the reaction between calcium carbonate and dilute nitric acid. ......................................................................................................................................[1] (b) Had the reaction between calcium carbonate and nitric acid finished after 20 minutes ? Explain your answer. .......................................................................................................................................... ......................................................................................................................................[1] (c) The experiment was repeated using a 3.0 g lump of calcium carbonate but an excess of 2.0 mol/dm3 nitric acid. Draw on the graph above, the curve you would expect. Label the curve X.

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[1]

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8 (d) Suggest why it is difficult to investigate the rate of reaction in this experiment using powdered calcium carbonate instead of a lump. ......................................................................................................................................[1] (e) Draw a labelled diagram to show another method of investigating the rate of reaction between nitric acid and a lump of calcium carbonate.

[3]

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For Examiner’s Use

For Examiner’s Use

9 SECTION B Answer three questions from this section. The total mark for this section is 30. B8 Methane is a fuel. It completely burns to form carbon dioxide and water. When one mole of methane is burned, 890 kJ of energy are released. H H

C

H H

+ 2 O = O → O = C = O + 2

H O

H (a) Calculate the energy released when 0.32 g of methane is burned.

[2]

(b) Use ideas of bond breaking and bond forming to explain why the reaction is exothermic. [3] (c) Name the products of the incomplete combustion of methane.

[1]

(d) Draw the ‘dot and cross’ diagram to show all the electrons in a molecule of methane. [2] (e) Give either the names or the structural formulae of two products of the reaction between chlorine and methane. [2]

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For Examiner’s Use

10 B9 Some information about four elements, W, X, Y and Z is shown in the table. element number of electrons in outer shell

W

X

Y

Z

4

1

1

1

density in g/cm3 melting point in °C

2.22

8.9

0.9

11.3

3720

1083

64

328

atomic radius in pm

77

135

203

154

ions formed

W 4+

X+ and X2+

Y+

Z2+ and Z4+

formulae and appearance of chlorides

WCl4 - a colourless liquid

XCl - a white solid XCl2 - a green solid

YCl - a white solid

ZCl2 - a white solid ZCl4 - a colourless liquid

(a) Y reacts with dilute sulphuric acid to give hydrogen. Construct the equation for this reaction. [1] (b) Which one of the elements is a transition element? Give three pieces of evidence from the table to support your answer.

[3]

(c) Copper and iron are transition elements. (i)

Describe the bonding in metals.

[2]

(ii)

Explain, in terms of metallic bonding, why copper and iron are good electrical conductors and are malleable. [2]

(d) Compare the action of steam on copper and on iron.

[2]

B10 Fats and oils are compounds formed by the reaction between carboxylic acids and an alcohol. The general formula for a saturated carboxylic acid is CnH2n+1COOH. (a) What type of compound are fats and oils?

[1]

(b) A diet containing unsaturated fats is healthier than one containing only saturated fats. (i)

What is the meaning of the term unsaturated ?

(ii)

Suggest a chemical test that could be used to show whether a fat is saturated or unsaturated. Name the reagent used and state the observations that would be made with the unsaturated and the saturated fat.

(iii)

Are fats made from stearic acid, C17H35COOH, or oleic acid, C17H33COOH, more healthy in your diet? Explain your answer. [6]

(c) Describe how soaps are manufactured from fats.

[2]

(d) Name a synthetic polymer that contains the same linkage as a fat.

[1]

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11 B11 Diamond and silicon carbide are both macromolecules. Part of the structure of silicon carbide is shown below.

For Examiner’s Use

C Si

C

C

C

(a) (i) (ii)

State one difference between the structures of silicon carbide and diamond. State one similarity between the structures of silicon carbide and diamond.

(b) Suggest two physical properties of silicon carbide.

[2] [2]

(c) Silicon carbide is manufactured by the reduction of silicon dioxide with carbon. SiO2 + 3C → 2CO + SiC (i)

State one source of silicon dioxide.

(ii)

What mass of carbon is needed to make 20 tonnes of silicon carbide?

[4]

(d) Silicones are polymers that contain the elements silicon, oxygen, carbon and hydrogen. Suggest the names of three combustion products of a silicone polymer.

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[2]

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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

150

Sm

Pu 94

Plutonium

62

152

Eu

Am 95

Americium

63

Europium

78

Platinum

Pt

Iridium

195

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

12