SuppEx Solution 3A E UncorrectedProof - 複製

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Topic 7 Fossil Fuels and Carbon Compounds

Part A Unit-based exercise

Unit 25 Fossil fuels

Fill in the blanks

1 coal; petroleum; natural gas

2 natural gas; marine

3 a) alkanes

b) cycloalkanes

c) aromatic hydrocarbons

4 fractional distillation

5 oil refinery; fractionating towers

6 naphtha

7 liquefied petroleum gas

8 Bitumen

9 Diesel oil

10 Fuel oil

11 exothermic

12 greenhouse

13 a) carbon monoxide

b) hydrocarbons

c) suspended particulates

d) oxides of nitrogen

14 nitrogen dioxide; sulphur dioxide

15 photochemical smog .

16 desulphurization; scrubbers

17 electrostatic precipitators

18 a) nitrogen

b) carbon dioxide

c) carbon dioxide; water


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2

True or false

19 T

20 T

21 F Refinery gas is a gas while bitumen is a solid.

22 F

23 T

24 T

25 F

26 T

27 T

28 F

29 T

30 F

31 F

32 F In the catalytic converter, unburnt hydrocarbons are mixed with air and oxidized to water and carbon

dioxide.

33 F Scrubbers can remove up to 95% of sulphur dioxide from the flue gas of a factory.

Multiple choice questions

34 C Option A — Coal is a solid while natural gas is a gas.

Option B — Coal is formed from plants that lived millions of years ago.

35 C

36 A

37 B

38 B

39 D


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40 A The fraction containing hydrocarbons with the smallest number of carbon atoms in their molecules has

the lowest boiling point range.

41 C

42 B Option A — Fraction 1 is lighter in colour than fraction 3.

Option C — Fraction 5 burns less easily than fraction 3.

Option D — Fraction 6 burns with a sooty flame.

43 B

44 D Fraction 7 is bitumen.

45 A

46 B

47 B

48 D

49 A Carbon monoxide combines with haemoglobin much more strongly than oxygen does. When carbon

monoxide enters the blood, haemoglobin is used up in the combination with carbon monoxide. The

blood can no longer carry sufficient oxygen to various parts of the body. The person thus feels dizzy.

50 A

51 C Car exhaust gas is acidic.

52 D

53 C

54 A Option C — Air pollutants such as oxides of sulphur and nitrogen react with rainwater to form acids,

lowering the pH value of rainwater. This gives rise to acid rain.

55 B

56 D

57 C A tall chimney cannot reduce the emission of pollutants.

58 A Oxides of nitrogen react with carbon monoxide as they pass through the catalyst in a catalytic

converter. Nitrogen and carbon dioxide are formed.

catalyst 2CO(g) + 2NO(g) N2(g) + 2CO2(g)


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4

59 C

60 B

61 B (1) Petroleum burns with a sooty flame.

(3) The constituents of petroleum can be separated into different groups by fractional distillation.

62 C

63 A

64 D

65 C (2) When the number of carbon atoms in molecules of a petroleum fraction increases, the fraction

burns with a more sooty flame.

66 B Fractions containing hydrocarbons with a smaller number of carbon atoms in their molecules have

lower boiling point ranges. They burn with clearer flames. Fractions containing hydrocarbons with agreater number of carbon atoms in their molecules have higher boiling point ranges. They burn with

sootier flames.

(1)Fraction Boiling point range

X lowest

Y middle

Z highest

(2) The viscosity of fraction Z is the highest.

67 D

68 D

69 D

70 D

71 C (3) When a gaseous fuel leaks, it forms a mixture with air. The mixture can be dangerously explosive.

72 C (1) Photochemical smog occurs through a series of reactions involving unburnt hydrocarbons and oxidesof nitrogen.

(2) Sulphur dioxide is a cause of acid rain. It reacts with rainwater to form acid that lowers the pH

value of rainwater.

SO2(g) + H2O(l) H2SO3(aq)

sulphurous acid

73 A


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74 A

75 B (1) Catalytic converters reduce the emission of nitrogen dioxide which can cause acid rain.

(2) Electrostatic precipitators can remove particulates. However, particulates do not cause acid rain.

(3) Using fuels of low sulphur content in factories reduces the emission of sulphur dioxide which can

cause acid rain.

76 D (1) Air pollution caused by sulphur dioxide can be reduced by using fuels with a low sulphur content.

(3) Scrubbers can remove up to 95% of sulphur dioxide from power station gas.

77 A

78 A

79 B Wood is not a fossil fuel.

80 C

81 D

82 B

83 C High-boiling petroleum fractions are more viscous than low-boiling petroleum fractions.

84 A

85 C

86 B

87 D

Unit 26 Homologous series, structural formulae and naming ofcarbon compounds

Fill in the blanks

1 structural

2 functional

3 hydroxyl

4 homologous

5 CnH2n+2


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6

6 CnH2n

7 14

8 methane

9 ethene

10 methanol

11 molecular

12 general

True or false

13 T

14 F Members in the same homologous series have the same general formula.

15 T

16 F

17 F Ethene is the first member of the alkene series.

18 F

19 F The molecular formula of both but-1-ene and but-2-ene is C4H8.

20 T

21 F

22 T

23 F

24 T

25 T

26 F


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27 C Members in a homologous series show the following characteristics:

• They have the same general formula, not the same molecular formula.

• Each member in a homologous series differs from the next by a —CH2— unit, not a —CH3— unit.

• They show a gradual change in physical properties.

• They show similar chemical properties, not the same chemical properties.

28 C Homologous series Functional group

Alkane —

Alkene C C

Alkanoic acid

O

C O H

29 C

30 B

31 D

32 A

33 A

34 C

35 A

36 B

37 B

38 B

39 C The general formula of alkane is CnH2n+2.

40 B

41 A

42 A The main carbon chain is a butane chain.

43 D


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8

44 C

45 D

46 A

47 C

48 B

49 D

50 A

51 D

52 D

53 C

54 C

55 B

56 B

57 B

58 C

59 B

60 A

61 D

62 A

63 B

64 C

65 D Members in the same homologous series have similar chemical properties and the same general

formula.

66 A

67 B The correct explanation is that they have the same general formula CnH2n+2.


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68 B

69 A

70 C

71 B

72 C

Unit 27 Alkanes and alkenes

Fill in the blanks

1 unsaturated

2 alkanes

3 combustion

4 substitution

5 a) initiation

b) propagation

c) termination

6 haloalkane

7 radical

8 cracking

9 addition

10 a) orange

b) 1,2-dibromoethane

True or false

11 F

12 T

13 T

14 T

15 F


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10

16 T

17 F

18 F During the cracking process, alkanes are heated in the absence of air. Otherwise, the alkanes will burn.

19 T

20 F

21 T

22 T

23 F

24 F

25 T

26 F


27 B Option A — Successive members differ by a —CH2— unit.

Option C — Melting points of alkanes increase as the number of carbon atoms in the alkane

molecules increases.

Option D — Alkanes undergo substitution reaction with halogens.

28 C

29 A The compound is ethane. It is the second member of the alkane series.

30 A

31 A

32 C The presence of tiny carbon particles makes the flame yellow.

33 B

34 C

35 B Option B — The reaction is a substitution reaction.

Option D — Chlorine is more reactive than bromine. Therefore the reaction between ethane and

chlorine is faster than that between ethane and bromine.


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36 C The compound is butane.

Option A — Its molecular formula is C4H10.

Option B — It cannot undergo addition reactions.

Option D — It cannot undergo polymerization.

37 C

38 B

39 A Cracking is the breaking down of larger hydrocarbon molecules with heat or catalyst to produce

smaller hydrocarbon molecules.

40 B

41 B

42 C The compound shown is ethene. It undergoes addition reaction with bromine dissolved in an organicsolvent.

43 D

44 B

45 A

46 D

47 D

48 CMolecular formula Compound Saturated / unsaturated

C3H6 propene unsaturated

C4H10 butane saturated

The compounds belong to different homologous series.

49 C

50 C Option A — Wind energy is not reliable as wind does not always blow.

Option B — Thousands of windmills are needed to provide enough electricity. Windy spots are often in

beautiful areas. Windmills may become an eyesore.

Option D — Not every part of the world has such strong wind.

51 B

52 A


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53 B Option A — The gaseous product burns easily while medicinal paraffin is difficult to burn.

Options B & D — The gaseous product contains a mixture of alkanes and alkenes.

Option C — The gaseous product has a pungent smell.

54 A (1) The first few cm3 of gas collected is mainly air.

(2) The medicinal paraffin may just vaporize and escape before cracking takes place when it is heatedcontinuously.

(3) Remove the delivery tube from the water before heating is stopped to avoid sucking back.

55 B

56 C

57 D

58 D

59 B

60 C

61 B Compound X is propane while compound Y is butane.

(2) They are saturated compounds. They would not decolorize acidified potassium permanganate

solution.

62 A (1) The two compounds have the same molecular formula C5H12. Therefore they have the same relative

molecular mass. (2) They are alkanes.

63 B (2) Surplus fractions (such as lubricating oil) are turned into fractions in greater demand (such as petrol)

during the cracking process.

64 D (1) Complete combustion of ethene gives carbon dioxide and water.

(2) Industrial ethanol is generally produced by catalytic hydration of ethene.

(3) Ethene can undergo polymerization to give polythene.

65 D

66 A The compound is propene. Chemical properties of propene are similar to that of ethene.

67 A

68 B

69 C


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70 C (1) Ethene and ethyne belong to different homologous series.

(3) Ethyne (C2H2) has a higher percentage by mass of carbon than ethane (C2H6). Therefore it burns

with a more sooty flame.

71 D

72 B Incomplete combustion occurs when the oxygen supply is limited.

73 A

74 C

75 D

76 C

77 D

78 C

79 B But-1-ene and but-2-ene can decolorize acidified potassium permanganate solution because they are

unsaturated.

80 B The correct explanation is that propene contains a functional group while propane is a saturated

hydrocarbon which is unreactive.

81 C Wind energy is costly to use.

82 D

Unit 28 Addition polymers

Fill in the blanks

1 polymer

2 polymerization

3 repeating unit

4 plasticizer

5 non-biodegradable

6 a) landfilling

b) incineration

c) recycling

d) pyrolysis


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14

True or false

7 F Thermoplastics are flammable.

8 T

9 F

10 T

11 T

12 F

13 T

14 T

15 F Handles of frying pans need to withstand high temperatures. They should be made from thermosetting

plastics.

16 T

17 F

18 T

19 T

20 F Most plastics are non-biodegradable.


21 B

22 D

23 A

24 D

25 C

26 C

27 D


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28 B

29 D

30 B

31 A

32 A

33 C

34 A

35 D

36 D The false teeth will be digested by bacteria in the mouth.

37 C Option A — Polyvinyl chloride is an addition polymer.

Option B — Polyvinyl chloride is made from chloroethene.

Option D — The repeating unit of polyvinyl chloride is C

H H

Cl H

C .

38 D

39 B

40 A

41 D

42 A The structure of polystyrene can be represented as C

H n

H H

C6H5

C .

43 C

44 A Plastic X is Perspex.

Option B — Perspex is strong and rigid. Option C — Perspex is rigid and highly transparent. It is not used to make rain coats. Polyvinyl chloride

is commonly used to make rain coats.

45 A

46 B


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47 B

48 B The repeating unit of polyvinyl chloride is C

Cl H

H H

C .

The relative molecular mass of one PVC repeating unit = 2 x 12.0 + 3 x 1.0 + 35.5

= 62.5

Number of PVC repeating units in one molecule =42 500

62.5

= 680

49 D

50 B

51 A

52 A

53 D

54 C

55 C (1) Most plastics are non-biodegradable.

56 B

57 B

58 C (2) & (3) Perspex is strong, rigid and highly transparent. It is used as a glass substitute.

59 C

60 A

61 C

62 A (3) Thermoplastics can be remoulded easily.

63 D

64 D

65 C

66 A


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67 C

68 C

69 A

70 B

71 D

72 A

73 D


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18

Part B Topic-based exercise


1 C Option A — Fraction 1 contains hydrocarbons with a small number of carbon atoms in their molecules.

It burns with a clear flame.

Option B — Fraction 2 contains hydrocarbons with a smaller number of carbon atoms in their

molecules when compared with fraction 3. Therefore fraction 2 is less viscous than fraction 3.

Option C — Fraction 3 contains hydrocarbons with a smaller number of carbon atoms in their

molecules when compared with fraction 4. Therefore fraction 3 burns more easily than

fraction 4.

Option D — Fraction 1 contains hydrocarbons with a smaller number of carbon atoms in their

molecules when compared with fraction 4. Therefore fraction 1 evaporates more easily

than fraction 4.

2 A

3 A Fraction P is refinery gases.

4 D

5 C Among the four given fractions, kerosene contains hydrocarbons with the smallest number of carbon

atoms in their molecules. Therefore it burns most easily.

6 C

7 B

8 D Inside power station furnaces, the air gets so hot that its nitrogen and oxygen react together, forming

oxides of nitrogen.

9 D

10 B Option B — An electrostatic precipitator removes up to 99% of the particulates. Dirty gases pass

through a strong electric field, where the particulates become charged. The charged

particulates then collect on plates of opposite charge.

Option D — A tall chimney cannot reduce the emission of air pollutants.

11 C

12 C

13 C

14 B


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15 A

16 A

17 D

18 A

19 C

20 B Option A — They are saturated compounds. They would not undergo addition reaction.

Option C — Diesel oil contains hydrocarbons with 14 – 25 carbon atoms per molecule. The two

compounds are not major components of diesel oil.

Option D — They are alkanes and have the same general formula CnH2n+2, not structural formula.

21 D

22 D

23 D

24 C

25 C

26 D

27 C

28 D

29 B

30 B

31 A

32 D

33 B

34 B

35 D

36 C


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20

37 A

38 A

39 B

40 C

41 A

42 C

43 C

44 A

45 A

46 A

47 D

48 A (1) Excessive burning of fossil fuels leads to acid rain. Rivers and lakes become more acidic. This is

harmful to water lives and even kills them.

(2) Photochemical smog occurs as a brown haze. It reduces visibility, causes eye and bronchial irritation,

and damage to plants and animals.

(3) Excessive intake of alcoholic drinks regularly may lead to liver damage.

49 B

50 C

51 C

52 B

53 B

54 B

55 C

56 A

57 C

58 A


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59 D

60 D

61 B The equation represents a cracking process.

C10H22 C8H18 + C2H4

(2) Cracking requires heat.

(3) X is ethene.

62 B

63 D

64 C

65 A

66 A

67 D

68 B

69 A

70 C (1) Nylon is usually used to make strings for tennis rackets because it is strong.

71 D Polystyrene is transparent, brittle and hard. It is commonly used to make ‘see-through’ containers, suchas milk feeding bottles.

72 D

73 C

74 D Plastic X is polypropene.

75 C Plastic X is polystyrene.

(1) The monomer of X is

H C6H5

C

H H

C .

(2) Polystyrene is a thermoplastic and can be remoulded.

76 D


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101 D

102 A

Short questions

103

ClassExample

Structural formula Systematic name

Alkanes any alkane

(1)

name of the alkane shown

(1)

Cycloalkanes /

H

H

H

H

H

H

H

H

C

C C

C

C

H H

C H

H

H

H

H

H

H

H

H H

H H

C

C

C

C

C

/ other appropriate cycloalkane

(1)

cyclopentane /

cyclohexane /

name of the cycloalkane shown

(1)

Aromatic

hydrocarbons

C

H

C

H

C C

C C

H

H H

/

H C

H

C

C

C C

C

HH

H

C

H

H H

H

/ other appropriate aromatic hydrocarbon

(1)

benzene /

methylbenzene /

name of the aromatic hydrocarbon

shown

(1)


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24

104

105 a) A, C, E and F (0.5 each)

b) A and E (0.5 each)

c) F (1)

d) A and E (1)

e) Hydroxyl group (1)

f) Carboxyl group (1)

g) i) C (1)

ii)

C

H H

CH3

C

H

(1)

h) A: 2,2-dimethylbutane (1)

B: propan-1-ol (1)


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C: propene (1)

D: pentanoic acid (1)

E: propane (1)

F: methylbenzene (1)

106 Structure IUPAC name

(a) CH3(CH2)3CH3 pentane

(1)

(b)

CH3

CH3

H C

H

H

C

H

CH3

C H 2,3-dimethylbutane

(1)

(c)

H C

H

H

C

H

CH2

CH3

CH3

C

H

H

3-methylpentane

(1)

(d)

H C

H

H H

C

H CH2 CH3

C

H

H

C

H

CH3

C

H

C

H

H

H

3-ethyl-2-methylhexane

(1)

(e)

CH3 CH2

H C

H

H

C

H

H

C

H

C

H

CH3

C

H

H

C

H

H

C

H

H

C

H

H

H

4-ethyl-3-methyloctane

(1)

(f)

CH3

methylcyclohexane

(1)

(g)

benzene

(1)

(h)

CH3

H C

H

H H

C

H H

H H

C C C H 3-methylpent-2-ene

(1)


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26

Structure IUPAC name

(i)

CH2

CH2

CH3

H C

H

H H

C

H

H

C

H

H

C

H

H

C

H

C CH

H

2-propylhept-1-ene

(1)

(j)

H C

H

H H

C

H

C

O H

H

C

H

H

H

butan-2-ol

(1)

(k)

CH2

CH3

CH3

H C

H

H

C

H

H H

C C

H

O H

2,3-dimethylpentan-1-ol

(1)

(l)

OH

hexan-3-ol

(1)

(m)

H C

H

H

C

H

CH3

C

O

O H methylpropanoic acid

(1)

(n)

H C

H

H

C

H H

CH2

CH3

C

H

H

C

H

C O H

O

4-methylhexanoic acid

(1)

(o)

Cl C

H

H H

C

H

H chloroethane

(1)

(p)

H C

H

H H

C

H Br

C

H

H

C

H

H 2-bromobutane

(1)


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Structure IUPAC name

(q)

CH3

3-methylcyclopentene

(1)

(r)

H C

H H

H

H

C

Br

H

C C H

3-bromobut-1-ene

(1)

107

Compound Structural formula

(a) butane

H C

H

H H

H

H

C C

H

C

H

H

H

(1)

(b) 2,2-dimethylpentane

CH3

CH3

H C

H

H H

C

H

H

C C

H

C

H

H

H

(1)

(c) 3-ethyl-2-methylheptane

CH 2

H C

H

H H

C

H

H

C

H H H

H

C C

H

CH3

CH3

C C

H

H

H

(1)

(d) 4-ethyl-2,5-dimethyloctane

CH3

H C

H

C C

H H H H H

H CH 2

C

CH3

CH3

C C

H

H

C

H

H

C

H

H

H

(1)


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28

Compound Structural formula

(e) cyclopentane

H

H

H

H

H

H

H

H

C

C C

C

C

H H

(1)

(f) but-2-ene

H C

H H H

C C

H

C

H

H

H

(1)

(g) 4,4-dimethylhex-1-ene

CH3

CH3

H C

H H

C

H

H

C C C

H

H

C

H

H

H

(1)

(h) hexan-2-ol

OH

H C

H

H H

H

H

C C

H

C

H

H

C

H

C

H

H

H

(1)

(i) 3-methylpentan-1-ol

CH3

H C

H H

H H

C C

H

C

H

H

C

H

H

OH

(1)

(j) butanoic acid

H C

H H

H H H

C C

H

C

O

OH

(1)


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108 a) A functional group is an atom, or a group of atoms, which determines most of the properties of a

compound. (1)

b)Compound Systematic name

Formula of

functional groupHomologous series

CH3

H C

H

H H H

C

H

C C H 3-methylbut-1-ene

(1)

C C

(1)

alkene

(1)

H C

H

H H

C

O

C

H

H

H

H

propan-2-ol

(1)

O H

(1)

alkanol

(1)

H C

H

H H

C

H H

H H

C C

H

O

C O H pentanoic acid

(1)

O

C O H

(1)

alkanoic acid

(1)

109

(a) A hydrocarbon that rapidly decolorizes

bromine dissolved in an organic solvent

Any one of the following:

• CH 3CH 2CH=CH 2 (1), but-1-ene (1)

• CH 3CH=CHCH 3 (1), but-2-ene (1)

CH 3 l• CH 3C=CH 2 (1), methylpropene (1)

(b) An alkanol Any one of the following:• CH 3CH 2CH 2CH 2OH (1), butan-1-ol (1)

OH l• CH 3CH 2CHCH 3 (1), butan-2-ol (1)

CH 3 l• CH 3CHCH 2OH (1), methylpropan-1-ol (1)

(c) An alkanoic acid Any one of the following:

• CH 3CH 2CH 2COOH (1), butanoic acid (1)

CH 3 l• CH 3CHCOOH (1), methylpropanoic acid (1)

(d) A hydrocarbon that reacts with chlorine onlywhen exposed to sunlight

Any one of the following:• CH 3CH 2CH 2CH 3 (1), butane (1)

CH 3 l• CH 3CHCH 3 (1), methylpropane (1)


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30

110 a) Alkanes (1)

b) The candle burns with a yellow flame due to incomplete combustion. (1)

The yellow colour of the flame is due to the presence of tiny carbon particles. (1)

c) The hot molten wax causes the water to vaporize rapidly. (1)

The steam will cause the molten wax to spurt out. (1)

111 a) Petroleum (1)

b) LPG contains hydrocarbons with a smaller number of carbon atoms in their molecules. (1)

It burns more completely than diesel. (1)

112 a) The purple solution of cold acidified dilute potassium permanganate becomes colourless quickly. (1)

HH

HH

H C

H

C

H

H(aq)

O O

H H

C C (g) + [O] + H2O(l)

(1)

b) The orange solution of bromine becomes colourless quickly. (1)

H Br

H C

H

C

H

H

Br

C

H

H(g) + Br2 (in organic solvent) (in organic solvent)

H

H C

H

C

H

C

H

(1)

c) The reddish brown colour of the mixture fades. (1)

C3H8(g) + Br2(g) C3H7Br(l) + HBr(g) (1)

113Product Advantage of using A over B Advantage of using B over A

(i) Toy bicycles

Polypropene

• is lighter in weight.

• does not corrode easily. any one(1)• is self-coloured.

• has no sharp edges.

Mild steel is stronger.

(1)

(ii) Sheets for packaging

Polythene is

• more durable.any one

(1)• stronger.

• waterproof.

Paper

• is biodegradable.any one

(1)• can be made from

renewable materials.


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Product Advantage of using A over B Advantage of using B over A

(iii) Drain pipes

PVC

• does not corrode

easily. any one

(1)• can be shaped more

easily.

Iron is stronger.

(1)

(iv) Lenses

Perspex is

• not easily broken. any one

(1)• lighter in weight.

Glass is not easily scratched.

(1)

114 a) There was insufficient oxygen for the fuel to burn completely. Carbon monoxide formed due to incomplete

combustion of fuel. (1)

Carbon monoxide is a very poisonous gas. (1)

b) A heptadecane molecule has a larger molecular mass / size (or a greater number of electrons) than a

heptane molecule. (1)

Therefore heptadecane has stronger van der Waals’ forces than heptane. (1)

Also heptadecane molecules in the form of long chains can become entangled. Hence the relative motion

between the molecules will be hindered. (1)

Therefore heptadecane is more viscous than heptane.

c) There are strong hydrogen bonds between water molecules. (1)

The weak attractions between molecules of alkanes and water are not strong enough to overcome the

strong attractions between water molecules. (1)

d) The shape of a heptane molecule is longer and more spread-out than that of a 2-methylhexane

molecule. (1)

The shape of heptane molecule allows greater surface contact between molecules. (1)

Thus the van der Waals’ forces in heptane are stronger than those in 2-methylhexane. (1)

Stronger van der Waals’ forces in heptane pull the molecules closer together.

Hence the density of heptane is higher than that of 2-methylhexane.

e) Polythene is a hydrocarbon with C–C and C–H bonds. These bonds are strong / not readily attacked by

chemicals. (1)


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32

Structured questions

115 a) Petroleum was formed from dead remains of marine animals and plants that lived millions of years

ago. (1)

High temperature, high pressure and bacterial action gradually changed the remains into petroleum. (1)

b) i) A hydrocarbon is a compound which contains only atoms of hydrogen and carbon. (1)

ii) A hydrocarbon in which all the carbon atoms are connected to each other by single bonds is a

saturated hydrocarbon. (1)

iii) The van der Waals’ forces between octane molecules are stronger than those between molecules of

the other compounds. (1)

iv) C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(l) (1)

v) Octane will burn with a more sooty flame. (1)

Octane has a higher percentage of carbon by mass. Its possibility of undergoing incomplete combustionto give carbon is higher. (1)

vi) To prevent excessive vaporization of petrol at high temperatures in summer, (1)

the petrol must contain more hydrocarbons with a greater number of carbon atoms in their

molecules. (1)

OR

To ensure adequate vaporization at low temperatures in winter, (1)

the petrol must contain more hydrocarbons with a smaller number of carbon atoms in their

molecules. (1)

c) • As fuels for generating electricity (1)

• As fuels for heating (1)

• As raw materials in the petrochemical industry (1)

116 a) A fractional distillation (1)

B cracking (1)

b) Change 1 liquid to gas / boiling / vaporization (1)

Change 2 gas to liquid / condensation (1)

c) i) As fuel for heavy vehicles / factories (1)

ii) As fuel for ships / power stations (1)

d) i) Diesel oil has a higher viscosity. (1)

Van der Waals’ forces between molecules in diesel oil are stronger than those between molecules in

petrol. (1)


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ii) Any three of the following:

• boiling point range (1)

• colour (1)

• volatility (1)

• flammability (1)

• clearness of flame when burnt (1)

e) Any two of the following:

• Biodiesel is renewable. (1)

• Use less fossil fuels / diesel. (1)

• Use waste oil. (1)

• Biodiesel is more biodegradable. (1)

• Biodiesel does not contain sulphur which causes the formation of acid rain. (1)

• Biodiesel burns with a less sooty flame. (1)

• The exhaust gas produced does not contribute much to global warming (burning biodiesel returns

carbon dioxide which has only recently been removed from the atmosphere during the photosynthesis

of plants). (1)

117 a) Petroleum originates from dead remains of marine animals and plants that lived millions of years ago.

(1)

b) i) Fractional distillation (1)

ii) It is because the components in petroleum have different boiling points. (1)

c) i) To condense the vapour given off into liquid. (1)

ii) To ensure that the temperature measured is exactly the boiling point of the vapour leaving the boiling

tube. (1)

iii) Any two of the following:

• Wear safety glasses and protective gloves. (1)

• Ensure good ventilation in the laboratory. (1)

• Avoid skin contact with the petroleum and its fractions as they may contain harmful substances.

(1)

• Ensure secure clamping of the apparatus. (1)

• Be careful of burns. (1)

• Avoid heating the mineral wool with a stationary hot flame. (1)

d) i) Fraction A burns with a less sooty flame than fraction B. (1)


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34

ii) Fraction A is less viscous than fraction B. (1)

iii) Molecules in fraction A are smaller than those in fraction B. (1)


• Petroleum is readily available at a relatively cheap price. (1)

• The production of electricity from petroleum is not dependent on the time of day, weather variations orseasonal effects. (1)

• Petroleum can be transported easily by pipeline, ship, road and rail. (1)

• Petroleum can be used to power cars. (1)

• Petroleum can be refined to provide raw materials for the production of other products, such as

plastics. (1)

f) i) Any three of the following:

• Burning of petroleum produces a lot of air pollutants. (1)

• The resource of petroleum is limited. (1)

• Supply and price of petroleum may be unstable in times of political unstability in petroleum-producing

countries. (1)

• Petroleum spills during drilling or transport cause major damage to ecosystems both on land and

at sea. (1)

ii) (1) Livestock manure (1)

(2) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) (1)

(3) Advantage:

• Biogas burns completely and produces no soot. (1)

Disadvantage:

• It reduces the amount of manure which can be used as fertilizers. (1)

118 a) Petroleum is first heated to about 400 °C in a furnace. The petroleum is turned into a mixture of liquid

and vapour. The mixture is then pumped into a fractionating tower. (1)

The liquid portion flows to the bottom of the tower and is collected as residue. (1)

The higher levels of the tower are cooler than the lower levels. (1)

The vapour portion rises up the tower and as it cools it turns back to liquid, collecting in trays at various

heights. (1)

b) As fuel for aircraft / as domestic fuel (1)

c) As fuel for heavy vehicles / factories (1)

d) i) Cracking is the breaking down of larger hydrocarbon molecules to produce smaller hydrocarbon

molecules. (1)


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ii) Producing extra petrol (1)

As a source of alkenes (1)

iii) Any one of the following:

• CH3CH2CH=CH2 (1)

but-1-ene (1)

• CH3CH=CHCH3 (1)

but-2-ene (1)

•

CH3

CH3C=CH2 (1)

methylpropene (1)

iv) Any one of the following:

• Mix with bromine dissolved in an organic solvent. (1)

The orange solution of bromine becomes colourless quickly when mixed with Y. (1)

The orange solution of bromine becomes colourless slowly when mixed with C16H34 under

sunlight. (1)

• Mix with cold acidified dilute potassium permanganate solution. (1)

The purple solution of potassium permanganate becomes colourless quickly when mixed with Y.

(1)

There is no observable change for C16H34. (1)

• Burn Y and C16H34 separately. (1)

Y gives less dark smokes. (1)

C16H34 gives more dark smokes. (1)

119 a) Fractional distillation (1)

b)

(1 mark for correct set-up; 1 mark for correct labels; 1 mark for correct fraction collection method; award

0 mark if the set-up is not workable) (3)


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36

c) i) The molecules in fraction 4 are larger / contain more electrons / have larger molecular masses than

molecules in fraction 1. (1)

Van der Waals’ forces between molecules in fraction 4 are stronger than those between molecules in

fraction 1. (1)

Molecules in fraction 4 have longer chains than molecules in fraction 1. The molecules tend to become

entangled. (1)

Hence fraction 4 is less runny / more viscous than fraction 1.

ii) Fraction 4 undergoes incomplete combustion. (1)

Molecules in fraction 4 have a higher percentage of carbon by mass. (1)

120 a) i) A photosynthesis (1)

B respiration (1)

C combustion / burning (1)

ii) Limestone / chalk / marble (1)

b) i) Photosynthesis and respiration / combustion (both parts must be correct for 1 mark) (1)

ii) Photosynthesis and fossil fuel formation (1) OR

Solution in water and limestone formation (1) (both parts must be correct for 1 mark)

c) i) The Earth receives energy from incoming sunlight and radiates energy back into space. (1)

Greenhouse gases can trap some of the infrared energy / heat radiated back into space. (1)

The heat keeps the atmosphere warm for life to sustain on Earth. (1)

ii) Increase in temperature of the atmosphere can cause melting of polar ice caps / flooding / change in

rainfall pattern. (1)


• Reduce the use of fossil fuel by using alternative energy sources to generate electricity, e.g. wind

energy. (1)

• Use hydrogen as fuel in fuel cells for cars. (1)

• Stop cutting down or burning forests. (1)

• Plant more trees. (1)

121 a) 2C9H20(g) + 19O2(g) 18CO(g) + 20H2O(l) (1)

b) i) High temperature / spark (1)

ii) N2(g) + O2(g) 2NO(g) (1)

c) i) They may cause cancer. (1)

ii) Irritate the respiratory system. (1)


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d) i) Nitrogen monoxide reacts with carbon monoxide as they pass through the catalyst in a catalytic

converter. Nitrogen and carbon dioxide are formed. (1)

2CO(g) + 2NO(g)catalyst

N2(g) + 2CO2(g) (1)

The excess carbon monoxide is oxidized to carbon dioxide by air. (1)

2CO(g) + O2(g) catalyst 2CO2(g) (1)

ii) The unburnt hydrocarbons are oxidized to water and carbon dioxide by air. (1)

2C8H18(l) + 25O2(g)catalyst

16CO2(g) + 18H2O(l) (1)

octane

e) Yes.

The hydrocarbons in diesel contain a much higher percentage of carbon by mass. (1)

Incomplete combustion will give a greater amount of particulates. (1)

122 a) i) Inside the car engine, the air gets so hot that nitrogen and oxygen react together, forming oxides of

nitrogen. (1)

ii) Irritate and attack the respiratory system / the lungs. (1)

iii) Nitrogen dioxide reacts with rainwater to form acids that lower the pH of rainwater. This gives rise to

acid rain. (1)

2NO2(g) + H2O(l) HNO3(aq) + HNO2(aq) (1)

iv) Catalytic converter (1)

b) i) Power stations burn either coal or low-grade petroleum, both containing sulphur. When these fuels

are burnt, they give off sulphur dioxide to the air. (1)

ii) Sulphur dioxide reacts with rainwater to form sulphurous acid. The acid lowers the pH of rainwater.

This gives rise to acid rain. (1)

SO2(g) + H2O(l) H2SO3(aq) (1)

iii) Flue gas desulphurization system / scrubber (1)

c) Any two of the following:

• It can cause surface waters and lakes to become too acidic.

This is harmful to water lives and even kills them. (1)

• Acid rain can cause damage to plants, including crops and forests. (1)

• Acid rain also damages metal / limestone structures.

It corrodes metals / wears away the limestone. (1)


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38

d) i) Any two of the following:

• Wind energy is a renewable energy source and hence will not run out like fossil fuels. (1)

• Wind energy produces no carbon dioxide and hence does not add to greenhouse effect. (1)

• Wind energy produces no sulphur dioxide and hence does not add to acid rain. (1)

• Less environmental impact of extraction / transport of fuels due to the decreasing use of fossilfuels. (1)

ii) (1) Any two of the following:

• Noise which may cause disturbance / stress. (1)

• Visual impact may deter tourists / spoil landscape beauty. (1)

• Risks to wildlife, e.g. bird strike. (1)

• Disruption to TV signals by interference. (1)

(2) Any one of the following:

• Further away from people (hence reduction of noise, visual impact, etc.) (1)

• Higher wind speeds / more wind (1)

123 a) The number of motor vehicles increases rapidly. Burning large amount of petrol / diesel produces carbon

dioxide. (1)

The rapid growth in population leads to deforestation, providing more land for housing. Less carbon

dioxide is removed from the atmosphere by photosynthesis. (1)

b) There is an increase in the number of rice paddies / cattle. The manure / remains decay to give

methane. (1)

c) The Earth receives energy from incoming sunlight and radiates energy back into space. (1)

Carbon dioxide and methane in the atmosphere can trap some of the infrared energy / heat radiated back

into space. (1)

d) Carbon dioxide is less soluble in oceans at higher temperatures. / The respiration of marine organisms

increases at higher temperatures. (1)

e) i) Any one of the following:

• Reduce the use of fossil fuel by using alternative energy sources to generate electricity, e.g. wind

energy. (1)

• Use hydrogen as fuel in fuel cells for cars. (1)

• Stop cutting down or burning forests. (1)

• Plant more trees. (1)

ii) Use natural gas / methane from biomass as a fuel. (1)


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124 a) i) A species containing an unpaired electron (1)

ii) O3 + •Cl ClO• + O2 (0.5)

O3 + ClO• Cl• + 2O2 (0.5)

overall equation 2O3 3O2 (1)

b) i) C7H16 (1)

ii) C7H16(g) + 11O2(g) 7CO2(g) + 8H2O(l) (1)

iii) Carbon particles / suspended particulates (1)

c) i) Traffic information / amount of nitrogen dioxide in air for more days. (1)

ii) Inside car engines, the air gets so hot that nitrogen and oxygen react together, forming oxides of

nitrogen. (1)

N2(g) + O2(g) 2NO(g) (1)

2NO(g) + O2(g) 2NO2(g) (1)

iii) Catalytic converter (1)

125 a) Any two of the following:

• Petroleum is readily available at a relatively cheap price. (1)

• The production of electricity from petroleum is not dependent on the time of day, weather variations or

seasonal effects. (1)

• Petroleum can be transported easily. (1)

• Petroleum can be used to power cars. (1)

• Petroleum can be refined to provide raw materials for the production of other products. (1)

b) i) Any two of the following:

• Pipeline breaches (1)

• Oil rig accidents (1)

• Illegal dumping (1)

• Tank washing (1)

• Loading / unloading spills (1)

ii) Any two of the following:

• Petroleum clogs the feathers of sea birds and prevents them from flying or swimming. (1)

• Petroleum is toxic and birds trying to clean their feathers with their beaks may be poisoned. (1)

• Petroleum interferes with the insulation provided by the feathers of sea birds. Birds may die of

cold. (1)


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• Petroleum floats on the water and blocks the oxygen supply to water lives. (1)

• Petroleum washed up on beaches can poison land animals which feed on beaches. (1)


• Contamination of water / beaches may deter tourists. (1)

• Contamination of fisheries reduces the value of catch / prevents fishing. (1)

c) This causes air pollution. (1)

d) • Use a boom to collect the spilt petroleum. Then the petroleum can be pumped out or absorbed. (1)

• Use detergent to break up the petroleum into small droplets. Then water current can carry the petroleum

away. (1)


• Members of the same homologous series have the same general formula. (1)

The general formula for pentane and decane is CnH2n+2. / Each member in a homologous series differs

from the next by a –CH2– unit. (1)

• Members of the same homologous series show a gradual change in physical properties. (1)

The boiling point / melting point / viscosity / density of decane is higher than that of pentane. (1)

• Members of the same homologous series show similar chemical properties. (1)

Both pentane and decane can undergo substitution reaction with bromine / chlorine. (1)

b) C14H30 (1)

c)

H C

H

H

C

CH3

H

C

H

H

C

H

H

H

(1)

2-methylbutane (1)

CH3

H C

H

H

C

CH3

C

H

H

H

(1)

2,2-dimethylpropane (1)

d) i) Any one of the following:

C10H22(l) C7H16(l) + C3H6(g) (1)

C10H22(l) C4H10(g) + 2C3H6(g) (1)

C10H22(l) CH4(g) + 3C3H6(g) (1)


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ii)

(1 mark for correct set-up; 1 mark for correct gas collection method; 1 mark for labelling of decane

and porcelain pieces; award 0 mark if the set-up is not workable) (3)

iii) Cold acidified dilute potassium permanganate solution (1)

It turns from purple to colourless quickly in the presence of propene. (1)

H OH

H C

H

C

H

H(aq)

OH

C

H

H(g) + [O] + H2O(l)

H

H C

H

C

H

C

H

(1)

iv) (1) CH3

C

H

H

C

H n (1)

(2) No. (1)

It does not contain carbon-carbon multiple bonds. (1)

127 a) i) The boiling points of alkanes rise as the number of carbon atoms in the alkane molecules increases.

(1)

ii) The boiling point of a compound depends on the strength of its intermolecular attractions. (1)

An alkane molecule becomes larger and heavier as the number of carbon atoms in the molecule

increases. The number of electrons in the molecule also increases. (1)

Hence the van der Waals’ forces between the molecules increase. (1)

Therefore more heat is needed to separate the molecules during boiling.

b) i) ~400 K (1)

ii) ~545 K (1)

c) i) A species containing an unpaired electron (1)

ii) Ultraviolet light / heat (1)

iii) C12H26 + Cl• C12H25• + HCl (1)

C12H25• + Cl2 C12H25Cl + Cl• (1)

iv) The reaction gives a mixture of products (C12H25Cl, C12H24Cl2, etc.). (1)


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42

128 a)Alkane Structural formula Systematic name

alkane W

CH3

H C

H

H

C

H

C

H

H

C

H

H

C

H

H

HC

H

H

(1)

2-methylhexane

(1)

alkane X CH3

H C

H

H

C

H

C

H

C

H

H

C

H

H

H

CH3

(1)

2,3-dimethylpentane

(1)

alkane Y

CH3

H C

H

H

C C

H

C

H

H

H

CH3CH3

(1)

2,2,3-trimethylbutane

(1)

alkane Z

H C

H

H

C

H

H

C

H

C

H

H

C

H

H

H

CH 2

CH3 (1)

ethylpentane

(1)

b) Y has the lowest boiling point. (1)

The boiling point of a compound depends on the strength of its intermolecular attractions. (1)

The shape of molecule of Y is most spherical and compact, thus there is the least surface contact between

molecules. (1)

Hence the van der Waals’ forces in Y are weakest. (1)

The least amount of heat is needed to separate the molecules of Y during boiling.

c) Any two of the following:

• CH3CH2CH2CH2CH2CH2CH3 (1)

heptane (1)

•

CH3

CH3CH2CHCH2CH2CH3 (1)

3-methylhexane (1)


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•

CH3

CH3

CH3CCH2CH2CH3 (1)

2,2-dimethylpentane (1)

•

CH3

CH3CHCH2CHCH3

CH3

(1)


•

CH3

CH3

CH3CH2CCH2CH3 (1)



• Clear flame (1)

• Easier to ignite (1)

• Easier to handle (1)

b) i) 2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(l) (1)

ii) • Carbon dioxide turns limewater milky. (1)

• Water turns blue cobalt(II) chloride paper pink. (1)

c) i) Very poisonous carbon monoxide gas may form. (1)

ii) 2C4H10(g) + 9O2(g) 8CO(g) + 10H2O(l) (1)

130 a) The reddish brown colour of the mixture fades. (1)

b) i) Substitution reaction (1)

ii) (1) Br••Br Br• + Br• (1)

(2) CH3CH3 + Br• CH3CH2• + HBr (1)

(3) CH3CH2• + Br2 CH3CH2Br + Br• (1)

iii) (1) Termination step (1)

(2) CH3CH2• + Br• CH3CH2Br (1) OR 2CH3CH2• C4H10 (1)

c) i) Fractional distillation (1)

ii) C2H6 + 6Br2 C2Br6 + 6HBr (1)

iii) Use excess bromine. (1)


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44

131 a) i) Methane is fully oxidized. (1)

ii) Carbon monoxide is a very poisonous gas. (1)

iii) Covalent bonding (1)

Dative covalent bonding (1)

b) i) Mix methane and chlorine gases in the presence of heat / ultraviolet light. (1)

Use a mixture of methane and chlorine in a mole ratio of 1 : 1. (1)

ii) Initiation (0.5)

Cl••Cl Cl• + Cl• (0.5)

Propagation (0.5)

CH4 + Cl• CH3• + HCl (0.5)

CH3• + Cl2 CH3Cl + Cl• (0.5)

Termination (0.5)

Any two of the following:

Cl• + Cl• Cl2 (0.5)

CH3• + Cl• CH3Cl (0.5)

CH3• + CH3• C2H6 (0.5)


• dichloromethane (0.5)

• trichloromethane (0.5)

• tetrachloromethane (0.5)

132 a) Crude oil is a mixture of alkanes with different boiling points. (1)

Heat the crude oil to obtain a mixture of liquid and vapour. (1)

Alkanes in the vapour portion condense at different temperatures. (1)

b) The C5 – C10 fraction is used as fuel for cars. (1)

c) i) C14H30 (1)

ii) C20H42 C14H30 + C3H8 + C2H4 + C (1)

iii) (1) The purple solution of cold acidified dilute potassium permanganate becomes colourless quickly.

(1)


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(2)

H

H

H

HH C

H

C

H

H(aq)

O O

H H

C C (g) + [O] + H2O(l)

(1)

(3) Addition reaction (1)

d) • Use different / lighter fractions. (1)

• Develop markets for the low demand fractions / develop new techniques to use the low demand

fractions as fuel for cars. (1)

• Develop alternative / bio fuels. (1)

133 a) CnH2n (1)

b)

H C

H

H

C

H

HC

H

(1)

H C

H

H

C

H

C

HH

H

C

H

H

C

H

HC

H

(1)

c) Any three of the following:

•

CH3

CH2=CHCHCH3 (1)

3-methylbut-1-ene (1)

• CH3CH=CHCH2CH3 (1)

pent-2-ene (1)

•

CH3

CH2CH=CCH3 (1)


•

CH3

CH2=CCH2CH3 (1)



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46

•

H

H

H

H

H

H

H

H

C

C C

C

C

H H

(1)

cyclopentane (1)

•

C C

CC

CH3

H

H

H

H

H

H

H

(1)

methylcyclobutane (1)

•

CH2CH3

H

H

H

C C

C

H H

(1)

ethylcyclopropane (1)

•

H3C CH3

HH

C C

C

H H

(1)

1,2-dimethylcyclopropane (1)

•

H3C

H3C

H

H

C C

C

H H

(1)

1,1-dimethylcyclopropane (1)

d) The boiling point of a compound depends on the strength of its intermolecular attractions. (1)

The strength of van der Waals’ forces in alkenes increases from ethene to hex-1-ene. (1)

Hence the boiling point increases from ethene to hex-1-ene.

e) There is hydrogen bonding in water. (1)

Alkene molecules cannot form hydrogen bonds with water molecules. (1)


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f) i) CH3

CH3

C C

H

H

(1)

ii) Methylpropene (1)

134 a) Cracking (1)

b)

(1 mark for correct set-up; 1 mark for correct gas collection method; 1 mark for labelling octane and

porcelain pieces; award 0 mark if the set-up is not workable) (3)

c) i) The products of cracking contained alkenes / unsaturated hydrocarbons (1)

which decolorized the bromine solution immediately by addition reaction. (1)

ii) The products of cracking also contained alkanes / saturated hydrocarbons (1)

which decolorized the bromine solution slowly by substitution reaction. (1)

135 a) A is hexane. (1)

C is hexan-2-ol. (1)

b) i) Mix hex-1-ene with bromine dissolved in an organic solvent. (1)

ii) The orange colour of the bromine solution becomes colourless quickly. (1)

c) i) It contains C=C bond. (1)

ii)

CH3(CH2)3

C

H

C

H

H

n

n

CH3(CH2)3

C C

H

HH

(1)

iii) Polyhex-1-ene (1)

iv) A plastic that can be melted or softened by heat. / A plastic that can be remoulded when warmed.

(1)


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48

d) Any two of the following:

C2H5

C C

CC

CH3

CH3

H

H

H

H

H

H

C H

H

HH

H

H

HH

H H

H H

C

C

C

C

C

C C

CC

C2H5

H

HH

H

H

HH

C C

CC

CH3

CH3

H

H

H

H

H

H

H

H

H

H

H

H

H

H

C

C C

C

C

H CH3

(1) (1) (1)

(1) (1) (1)

CH3

H

H

HC C

C

H

(other appropriate structural formulae are acceptable)

136 a) i) The orange colour of the bromine solution becomes colourless quickly. (1)

ii) Addition reaction (1)

iii) C10H16 + 3 (1) Br2 C10H16Br6 (1)

b) Compound Y has a higher boiling point. (1)

The boiling point of a compound depends on the strength of its intermolecular attractions. (1)

Compared with molecules of X, molecules of Y are longer and somewhat spread-out. (1)

This allows greater surface contact between molecules of Y. (1)

The van der Waals’ forces in Y are thus stronger. Hence the boiling point of compound Y is higher.

c)

C

H

X

C

H

H (1)

137 a) i) Mass of carbon present in 0.0150 mole of X

= 3.30 g x12.0

44.0

= 0.900 g

Mass of carbon present in 1 mole of X

=0.900 g

0.0150 mol

= 60.0 g (1)


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ii) Mass of hydrogen present in 0.0150 mole of X

= 1.35 g x2.0

18.0

= 0.150 g

Mass of hydrogen present in 1 mole of X

=0.150 g

0.0150 mol

= 10.0 g (1)

iii) Number of moles of carbon in 1 mole of X

=60.0 g

12.0 g mol–1

= 5.00 mol (0.5)

Number of moles of hydrogen in 1 mole of X

=10.0 g

1.00 g mol–1

= 10.0 mol (0.5)

∴ the molecular formula of X is C5H10.

b)Structure of X Systematic name of X

Structure of product formed

between X and bromine


CH 3CH 2CH 2CH=CH 2 (1)

CH 3CH 2CH=CHCH 3 (1)

CH 3 CH 3CH 2C=CH 2 (1)

CH 3 CH 3CHCH=CH 2 (1)

CH 3 CH 3C=CHCH 3 (1)

pent-1-ene (1)

pent-2-ene (1)



methylbut-2-ene (1)

CH 3CH 2CH 2CHBrCH 2Br (1)

CH 3CH 2CHBrCHBrCH 3 (1)

CH 3 CH 3CH 2CBrCH 2Br (1)

CH 3 CH 3CHCHBrCH 2Br (1)

CH 3 CH 3CBrCHBrCH 3 (1)

138 a)Name Molecular formula Condensed structural formula

Ethene C2H4 CH2=CH2

Propene (0.5) C3H6 CH 3CH=CH 2 (0.5)

But-1-ene C 4H 8 (0.5) CH 3CH 2CH=CH 2 (0.5)

But-2-ene (0.5) C 4H 8 (0.5) CH3CH=CHCH3

Pent-1-ene (0.5) C 5 H 10 (0.5) CH3CH2CH2CH=CH2

Pent-2-ene C 5 H 10 (0.5) CH 3CH 2CH=CHCH 3 (0.5)


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b) i) A family of compounds containing the same functional group is a homologous series. (1)


• Members of the same homologous series have the same general formula. (1)

The general formula for ethene and but-1-ene is CnH2n. / Each member in a homologous series

differs from the next by a –CH2– unit. (1)

• Members of the same homologous series show similar chemical properties. (1)

Both ethene and but-1-ene can undergo addition reaction with bromine dissolved in an organic

solvent / cold acidified dilute potassium permanganate solution. (1)

• Members of the same homologous series show a gradual change in physical properties. (1)

The boiling point of but-1-ene is higher than that of ethene. (1)

c) i) Cracking (1)

Breaking down of larger hydrocarbon molecules with heat or catalyst to produce smaller hydrocarbon

molecules. (1)

ii) Addition polymerization (1)

iii)

n C C

HH

HH

C

H

H

C

H

H n (1)

iv) High density polythene is a hydrocarbon with strong C–C and C–H bonds. (1)

These bonds are not readily attacked by chemicals.

d)

CH2

C

H

C

H

H

CH2

CH3

(1)

e) • Less waste / less landfill / easier to dispose of / less pollution from burning. (1)

• Does not use up crude oil. (1)

139 a) i) Any one of the following:

• Electricity leakage can be prevented. (1)

• Plastic does not corrode easily. (1)


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ii) Any one of the following:


• Plastic can be shaped more easily. (1)



• Lightweight. (1)

• No chrome plating required. (1)

iv) Any one of the following:


• Lightweight. (1)

• No sharp edges. (1)

• Self-coloured / no painting required. (1)

• More durable. (1)

b) i) (1) CH3

C C

HH

H

(1)

(2) Propene (1)

ii) • Addition polymerization (1)

• Moulding (1)

iii) Resistance to chemicals / barrier to moisture (1)

iv) Yes (1)

Plastic X is a thermoplastic (can be softened by heat) and thus can be remoulded. (1)

c) i) Landfilling


• Degradation of plastic takes a long time. (1)

• May cause pollution of underground water. (1)

• Slow release of toxins from landfill sites. (1)

Incineration

• Toxic gases are produced. (1)

ii) Recycling / pyrolysis (1)


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52

140Item

Plastic suitable for

making the item

Two properties of the plastic

that make it suitable

Repeating unit of

the plastic

(a) food wrap polythene

(1)


• soft and flexible (1)

• good resistance to chemical

attack (1)

• good moisture barrier

properties (1)

• does not flavour the food (1)

• non-toxic (1)

C

H

H

C

H

H

(1)

(b) bottle crate polypropene

(1)


• strong (1)

• lightweight (1)

• good resistance to chemical

attack (1)

• does not deform under heavy

load / stiff (1)

CH3

C

H

H

C

H

(1)

(c) shower

curtain polyvinyl chloride

(1)


• durable (1)

• easily coloured (1)

• flexible (1)

• does not wrinkle easily (1)

Cl

C

H

C

H

H

(1)

(d) transparent

advertising

display

Perspex

(1)


• strong (1)

• rigid (1)

• not easily scratched (1) CH3

CH3

C

H

C

C

H

O

O(1)


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141 a)Monomer Polymer

H

H

H

HC C

monomer A

C

H

H

C

H

H n

polymer A

Cl

H

H

HC C

monomer B

Cl

C

H

H

C

H n (1)

polymer B

F

F

F

F C C

(1)

monomer C

C

F

F

C

F

F n

polymer C

b) i) Any two of the following:

• Waterproof (1)

• Non-toxic (1)

• Stiff (1)

• Strong (1)

• Non-sticking (1)

• Does not crack when cold (1)

• Good resistance to chemical attack (1)

• Does not flavour the solution (1)

ii) It softens / changes shape when heated. (1)

iii) Polymer A is a hydrocarbon with C–C and C–H bonds. These bonds are strong / not readily attackedby chemicals. (1)

iv) Polymer A is a mixture of polymeric molecules of different chain lengths. (1)

v) In polymer A, the polymer molecules are in the form of separate long chains.

Only weak van der Waals’ forces hold the chains together. (1)

Upon heating, these forces are overcome and the chains move over one another. (1)


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c) i)

F C

F

F

C

F

C

F

F

(1)

ii)

C

F

CF3

C

F

C

F

FF

C

F

F

C

F

C

F

FF

(2)

(different order of residues is acceptable)

d) Any two of the following:

• Incineration can produce energy and the need for burning fossil fuels is reduced. (1)

• Landfilling may cause pollution of underground water. (1)

• There may be slow release of toxins from landfill sites. (1)

142 a) Process 1 Fractional distillation (1)

Process 2 Cracking (1)

Process 3 Fractional distillation (1)

b) i) It contains C=C bond. (1)

ii)

C

H

H

C

H

H (1)

iii) It is durable / light / chemically inert / waterproof. (1)

c) i) • Incineration (1)

• Pyrolysis (1)

• Landfilling (1)


• It reduces the amount of plastic waste. (1)

• It helps conserve petroleum which is non-renewable. (1)

• It converts plastic waste into useful products. (1)


• Difficult to separate plastic waste from other waste. (1)

• Difficult to separate different plastic waste. (1)


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• Difficult to remove additives in the plastic waste. (1)

• Many plastics lose their original properties over successive recycling cycles. (1)

• The cost is high. (1)

iv) Bring our own bags. / Use substitutes for plastics. / Reduce the use of plastics. / Use biodegradable

plastics. (1)

143 a) Polymerization is the process of repeatedly joining together many small molecules to form very large

molecules. (1)

b) Monomer A Cl

C C

HH

H

(1)

Monomer B

C C

H

HH

(1)

c) Polystyrene (1)

d) ClCl

n C C

HH

H

C

H

C

H

H n (1)


• Good insulator of electricity (1)

• Flexible (1)

• Easy to mould (1)

• Easy to colour (1)

• Waterproof (1)

f) i) To improve the heat insulating property of the material. (1)

ii) Making sample bottles / compact disc cases / yogurt pots (1)

g) i) • Hydrogen chloride can cause the formation of acid rain. (1)

• Hydrogen chloride can irritate and attack the respiratory system. (1)

ii) Pass the gas through a scrubber. (1)


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144 a) Any three of the following:

• Does not break when hit. (1)

• Does not corrode / does not react with moist air. (1)

• Not degraded by sunlight. (1)

• Does not dissolve in water. (1)

• Non-biodegradable (1)

• Lightweight (1)

• Thermal insulator (1)

• Durable (1)

• High melting point (1)

• Strong (1)

• Rigid (1)

b) i) A repeating unit is the smallest part of a polymer molecule, (1)

and the whole polymer structure can be obtained by repeating it. (1)

ii) CH3

CH3

C C

CH

H

O

O

(1)

iii) Addition polymerization (1)

iv) Glass substitute for advertising displays and illuminating signs / protective shields / car light covers (1)

145 a)

C C

H

HH

(1)

b)

n C C

H

HH

C C

HH

H n

styrene polystyrene (1)


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c)

(1 mark for correct set-up; 1 mark for correct direction of water flow in condenser; award 0 mark if the

set-up is not workable) (2)

d) As a solvent of styrene (1)

and as a catalyst. (1)

e) Any one of the following:

• Use an oil bath / a water bath / electric heating mantle for heating (1)

because kerosene is flammable. (1)

• Heat the mixture in a fume cupboard (1)

because styrene vapour is irritant. (1)

f) i) Any one of the following:

• Milk feeding bottle (1)

• Sample bottle (1)

• Transparent pitcher (1)

• Any other possible use (1)


Milk feeding bottle Sample bottle Transparent pitcher

• transparent (1)

• waterproof (1)

• can withstand the

temperature of boiling

water (1)

• rigid (1)

• easily shaped (1)

• chemically inert (1)

• non-toxic (1)

• does not flavour the

milk (1)

• transparent (1)

• rigid (1)

• lightweight (1)


• transparent (1)

• rigid (1)

• waterproof (1)


• chemically inert (1)

• non-toxic (1)

• does not flavour the

water / liquid (1)


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iv) Advantage: Conserve raw materials. / Useful products can be obtained. (1)

Disadvantage: A lot of energy is required. (1)

v) Any one of the following:

• Difficult to separate plastic waste from other waste (1)

• Difficult to separate different plastic waste (1)

• Many plastics lose their original properties over successive recycling cycles (1)

• Difficult to remove additives in plastic waste (1)

• The process is uneconomical (1)

147 a) Hydroxyl group (1)

Carboxyl group (1)

b) A polymer is a compound which consists of very large molecules (1)

formed by joining together many small molecules repeatedly. (1)

c) i) In a thermoplastic, the polymer molecules are in the form of separate long chains. Only weak

intermolecular forces hold the chains together. (1)

Upon heating, these forces are overcome and the chains move over one another. (1)

ii) Less waste / less landfill / easier to dispose of / less pollution from burning (1)

148 a) The Earth receives energy from incoming sunlight and radiates energy back into space. (1)

Greenhouse gases can trap some of the infrared energy / heat radiated back into space. (1) b) Any two of the following:

• carbon dioxide (1)

• methane (1)

• oxides of nitrogen (1)

• ozone (1)

c) Increase in temperature of the atmosphere can cause melting of polar ice caps / flooding / change in

rainfall pattern. (1)

d) Cl

Cl

F F

C

(1)

e) CF2Cl2 is not able to react with substances in the lower atmosphere, and thus it reaches the upper

atmosphere. (1)


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f) i) Free radical (1)

ii) Initiation (1)

iii) Propagation (1)

g) i)

F C

F

F

C

H

H

F

(1)

ii) It contains two H atoms and thus is more reactive than a CFC. (1)

149 a) Laundry bags do not have to be opened and thus prevent the spread of infectious microbes throughout

the hospital. (2)

b) A repeating unit is the smallest part of a polymer molecule, (1)

and the whole polymer structure can be obtained by repeating it. (1)

c) The –OH groups of the polymer chains of PVA can form hydrogen bonds with water molecules. (1)

d) Polymerization is the process of repeatedly joining together many small molecules to form very large

molecules. (1)

e) Farmers can drop powdered insecticides and herbicides packaged in PVA bags into water for preparing

the dilute solutions required. (The farmer is never exposed to the chemicals). (2)

f) Polythene (1)

150 a) The product obtained contains different plastics as well as other substances such as refuse. (1)

b) It is difficult to isolate polythene from other plastics as the plastics may have very similar densities. (1)

c) CH3

OR

benzene methylbenzene (2)

d) i) Economic argument


• Polythene waste must be collected / transported / sorted / washed; these processes areexpensive. (1)

• These processes use fossil fuels which are expensive. (1)

Environmental argument


• Using fossil fuels that are non-renewable / forms CO2 / CO / SO2 / NO x / particulates (1)

• Washing uses / pollutes water. (1)


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• Landfill is running out. (1)

• Polythene is non-biodegradable / degradation of polythene waste takes a long time. (1)

• Landfilling may cause pollution of underground water. (1)

• Slow release of toxins from landfill sites. (1)

• Collect / transport polythene waste alongside other waste. (1)

• Recycling helps conserve petroleum which is non-renewable. (1)

• Polythene waste can be converted into useful products. (1)

• More jobs / employment for local people. (1)

151 Our high standard of living is due to fossil fuel use.

Any three of the following:

Petrol and diesel oil obtained from the fractional distillation of petroleum are used as fuels to power

vehicles. (1)

Fuels are used to generate electricity. (1)

Refinery gases and kerosene obtained from the fractional distillation of petroleum are used for cooking and

heating. (1)

Petrochemicals serve as raw materials in the production of many synthetic substances, particularly a wide

range of plastics. (1)

However, burning fossil fuels causes global warming and serious air pollution problems.

Any three of the following:

Fossil fuel combustion produces carbon dioxide, a major greenhouse gas. Too much carbon dioxide in the

atmosphere can cause global warming. (1)

Most of the carbon monoxide in the air comes from the exhaust gas of cars, trucks and buses. Carbon

monoxide is a very poisonous gas. (1)

Not all the petrol in car engines gets burnt. Some unburnt hydrocarbons escape in the car exhaust gas.

Unburnt hydrocarbons give photochemical smog with oxides of nitrogen. (1)

Inside car engines, the air gets so hot that nitrogen and oxygen react together, forming oxides of nitrogen.

Oxides of nitrogen can cause the formation of acid rain. (1)

Incomplete combustion of hydrocarbons produce suspended particulates. These particulates can reduce

visibility. (1)

Combustion of coal or low-grade petroleum in factories and power stations produces sulphur dioxide. Sulphur

dioxide can cause the formation of acid rain. (1)

(3 marks for organization and presentation)


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152 Factories and power stations burn either coal or low-grade petroleum, both containing sulphur. When these

fuels are burnt, they give off sulphur dioxide to the air. (1)

Inside car engines and power station furnaces, the air gets so hot that nitrogen and oxygen react together,

forming oxides of nitrogen. (1)

Sulphur dioxide reacts with rainwater to form sulphurous acid. (1)

Nitrogen dioxide reacts with rainwater to form nitric acid and nitrous acid. (1)

These acids lower the pH of rainwater, giving rise to acid rain.

Measures to reduce acid rain formation

• For sulphur dioxide


– using low-sulphur coal instead of high-sulphur coal (1)

– installing flue gas desulphurization systems or scrubbers in power stations (1)

• For oxides of nitrogen


– installing catalytic converters in exhaust systems of motor vehicles (1)

– installing low nitrogen oxide burners in power stations (1)


153 Chemists balance the supply and demand of petrol by turning the surplus fractions (like fuel oil and lubricating

oil) into petrol. (1)

High-boiling fractions contain molecules larger than those in petrol. Chemists break the large molecules into

smaller ones by a process called cracking. (1)

During the cracking process, alkanes with large molecules are heated in the absence of air to a high

temperature. (1)

The alkane molecules move and vibrate faster. The molecules collide with one another with greater energy

as the temperature increases. Eventually the large alkane molecules have so much energy that they begin to

break up into small molecules. (1)

Alkanes with small molecules can be used as petrol. (1)

In an oil refinery, a catalyst is used to increase the rate of the cracking reaction. The method is called catalytic

cracking. (1)



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154 Most plastic waste in Hong Kong are treated by landfilling, others are recycled / incinerated.

Landfilling


• A lot of plastic waste can be treated in a short period of time. (1)

• Not enough land for building landfill sites. / The three strategic landfills in Hong Kong will soon be filledup. (1)

• Degradation of plastic takes a long time. (1)

• May cause pollution of underground water. (1)

• There is slow release of toxins from landfill sites. (1)


Recycling


• Conserve petroleum which is non-renewable. (1)

• Plastic waste can be converted to useful products. (1)

• It is difficult to separate plastic waste from other waste. (1)

• It is difficult to separate different plastic waste. (1)

• Many plastics lose their original properties over successive recycling cycles. (1)

• It is difficult to remove additives in plastic waste. (1)

• The process is uneconomical. (1)

Incineration


• Volume of solid waste can be greatly reduced. (1)

• Energy can be produced. (1)

• Reduce landwastage. (1)

• Toxic gases are produced. (1)

• The cost of operating a controlled incineration plant is high. (1)

How citizens can help reduce plastic waste problems

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