Oxford Revise AQA GCSE Chemistry | Chapter C14 answers

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AO / Specification reference

01.1

top = ethane

bottom = butane

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AO1

4.7.1.1

01.2

C₂₂H₄₆

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AO2

4.7.1.1

01.3

decane has a lower flammability, higher boiling point, and higher viscosity

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AO1

4.7.1.3

02.1

Points plotted at (5,36) (6,69) (7, 98) (8, 126) (10, 174) (11, 196) (12, 216)

two marks for all eight points correctly plotted

one mark for four to seven points correctly plotted

one mark for line of best fit

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AO2

02.2

153

allow number between 151 and 155

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AO3

02.3

C₉H₂₀ + 14O₂ → 9CO₂ + 10H₂O

one mark for correct formula of nonane

one mark for formulae of reactants

one mark for formulae of products

one mark for balancing

4

AO2

4.1.1.1

03.1

compounds in crude oil with a similar number of carbon atoms

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AO1

4.7.1.2

03.2

vapour moves up the column, cooling as moving up

fractions condense when they reach the temperature of their boiling points

different fractions collected at different levels

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AO1

4.7.1.2

03.3

Level 3: The comparisons are detailed and accurate. The writing is clear, coherent and logical and comparisons are clearly made.

5-6

AO1

4.7.1.3

Level 2: The comparisons are generally correct, although may lack detail. The writing is mainly clear, although the structure may lack logic and comparisons are not always clear.

3-4

Level 1: Some comparisons are correct. The writing lacks clarity, coherence and logic, and the comparisons are not clearly expressed.

1-2

No relevant content

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Indicative content

• both burn (completely) to make carbon dioxide and water
• on burning, both release energy/transfer energy to the surroundings
• diesel boils at higher temperatures than petrol
• diesel is more viscous than petrol
• diesel is less flammable than petrol
• diesel is more likely to have smoker/ more sooty flame

04.1

so that the liquid hydrocarbon forms vapour

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AO2

4.7.1.4

04.2

should not be in the liquid collected

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AO3

04.3

C₅H₁₂

boiling point increases with molecule size

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AO2

4.7.1.3

04.4

orange/brown to colourless

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AO1

4.7.1.4

05.1

B is C₂H₄ – bromine test shows it is an alkene

C is C₁₇H₃₆ – has highest boiling point so must have the biggest molecules

D is C₂H₆ – has lowest boiling point of the alkanes so has smallest molecules

A is C₈H₁₈ – intermediate boiling point of alkanes, and so intermediate size molecules

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AO3

4.7.1.3

4.7.1.4

05.2

C

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AO3

4.7.1.3

05.3

C₂₀H₄₂ → C₈H₁₈ + 4C₃H₆

one mark for formulae of reactants

one mark for formulae of products

one mark for balancing

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AO2

4.7.1.4

06.1

hydrocarbons

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AO1

4.7.1.2

06.2

fractional distillation

crude oil is vaporised and pumped into column

temperature decreases as you go up column

groups of hydrocarbons of a similar number of carbon

atoms condense at their boiling point

the fractions are tapped off

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AO1

4.7.1.2

06.3

one from

• petroleum gas – fuel
• petrol – fuel (in engines)
• kerosene – fuel (in aircraft)
• heavy fuel oil/diesel oil – fuel (diesel engines)
• residue/bitumen – making roads

use must match the fraction given

fuel on its own is an acceptable answer for petroleum gas, petrol, kerosene, and heavy fuel oil; however, if a particular machine is named it must match the correct fraction

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AO1

4.7.1.2

07.1

crude oil

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AO1

4.7.1.1

07.2

(6 × 12) + (14 × 1) = 86

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AO2

4.3.1.2

07.3

Level 3: The pattern is described correctly and the explanation is accurate. The writing is clear and coherent and the reasoning is logical.

5-6

AO1 × 2

AO3 × 4

Level 2: The pattern is correctly described, and the explanation mainly accurate. The writing is mainly clear and coherent, but the reasoning lacks logic.

3-4

Level 1: The pattern is described correctly. The writing lacks clarity and coherence. The reasoning is unclear.

1-2

No relevant content.

0

Indicative content

• alkanes consist of small molecules with weak intermolecular forces between the molecules
• boiling point decreases as intermolecular force strength decreases
• data in the table show that as the number of branches increases, boiling point decreases
• intermolecular bond strength decreases as branching increases

08.1

both require heat

in catalytic cracking, the vapour is passed over a hot catalyst

in steam cracking, the vapour is mixed with steam before heating

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AO1

4.7.1.4

08.2

C₁₀H₂₂ → C₆H₁₄ + 2C₂H₄

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AO2

4.1.1.1

08.3

to make more smaller alkane molecules for fuels

to make alkenes to produce polymers/other chemicals

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AO1

4.7.1.4

09.1

C₅H₁₂ + 😯₂ → 5CO₂ + 6H₂O

one mark for formulae of reactants

one mark for formulae of products

one mark for balancing

3

AO2

4.1.1.1

09.2

per mole of \(C_5H_{12}\) complete combustion requires 8 moles of oxygen but incomplete combustion requires \(\frac{11}{2}\) = 5.5 moles of oxygen

so incomplete combustion occurs when there is not enough oxygen for complete combustion

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AO3

4.7.1.3

09.3

energy to break bonds in reactants = (2 × 348) + (8 × 412) + (5 × 496)

= 6472 (kJ)

energy to make bonds in products = (6 × 743) + (8 × 463)

= 8162 (kJ)

energy change of reaction = 8162 – 6472 = 1690 (kJ)

ignore units

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AO1

4.5.1.3

10.1

positive – bubbles of gas/swimming pool smell/green gas formed

negative – small drops of silver-coloured metal

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AO2

4.4.3.2

10.2

Zn²⁺ + 2e⁻ → Zn

one mark for formulae of reactants

one mark for formulae of products

one mark for balancing

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AO2

4.4.3.5

10.3

positive – chlorine

negative – hydrogen

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AO2

4.4.3.4

11.1

reversible

allow description of reversible reaction

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AO1

4.6.2.1

11.2

cooling (the mixture of ammonia and hydrogen chloride)

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AO2

4.6.2.2

11.3

prevents the escape of reactants and products

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AO1

4.6.2.3

12.1

remains of ancient biomass/plankton that was buried in the mud

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AO1

4.7.1.1

12.2

evaporation

condensation

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AO1

4.7.1.2

12.3

Level 3: A range of products and their uses are described. The writing is clear and coherent.

5-6

AO1

4.7.1.2

Level 2: Some products and/or their uses are described. The writing is mainly clear and coherent.

3-4

Level 1: One or two products/uses are described. The writing lacks clarity and coherence.

1-2

No relevant content.

0

Indicative content

• fuels, for example diesel, petrol, kerosene, liquefied petroleum gases
• raw materials for solvents
• raw materials for lubricants
• raw materials for polymers
• raw materials for detergents

13.1

covalent bonds

shared pairs of electrons between neighbouring atoms

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AO1

4.2.1.4

13.2

intermolecular

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AO1

4.2.2.4

13.3

C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O

M_r of heptane = (7 × 12) + (1 × 16) = 100

from the equation, one mole of heptane makes seven moles of carbon dioxide

so 0.850 mol of heptane makes 0.850 × 7 = 5.95 mol of CO₂

M_r of carbon dioxide = 12 + (16 × 2) = 44

so mass of carbon dioxide = 5.95 × 44 = 262 g

= 260 g

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AO2