AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2022: Question 2

12 marks · Low Demand difficulty · Short Answer

Answer questions on fractional distillation of crude oil, trends in hydrocarbon properties, cracking, alkane formula and bonding, and complete combustion products.

Practise this question

Question

Question 02 consists of eight parts about crude oil and hydrocarbons. Part 02.1 presents Table 2 showing boiling point ranges for fractions A, B, and C, and Figure 1 showing a fractionating column with three outlet pipes to be labelled with the fractions. Part 02.2 provides Table 3 showing carbon chain lengths for petrol, diesel, and heavy fuel oil, with fill-in-the-blank sentences comparing viscosity and flammability. Part 02.3 provides Table 4 with percentage yields of kerosene and heavy fuel oil from sources J and K, asking to complete the y-axis scale and plot a bar for source K in Figure 2. Part 02.4 asks why source J is in higher demand. Part 02.5 asks to select two substances used to crack hydrocarbons. Part 02.6 asks to complete the formula for an alkane with 11 carbon atoms. Part 02.7 asks to identify the type of bond in ethane from a multiple-choice list. Part 02.8 asks to select the two products of complete combustion of alkanes.
Question text

02 This question is about hydrocarbons in crude oil.

02.1 Table 2 shows information about three fractions obtained from crude oil.

Table 2

Fraction Boiling point range in °C

A 200–300

B 100–150

C Below 30

Figure 1 shows the fractionating column used to separate fractions A, B and C.

Figure 1

The temperature of the fractionating column is:

• 30 °C at the top

• 400 °C at the bottom.

Complete Figure 1 to show where fractions A, B and C are collected.

[1 mark]

02.2 Table 3 shows information about three fractions obtained from crude oil.

Table 3

Range of number of

Fraction

carbon atoms in each molecule

Petrol 5–12

Diesel oil 15–19

Heavy fuel oil 20–40

Complete the sentences.

Choose answers from the box.

[2 marks]

lower the same higher

Compared to petrol, the viscosity of heavy fuel oil is .

Compared to petrol, the flammability of diesel oil is .

Table 4 shows the percentage of two fractions obtained from two different sources of

crude oil.

Table 4

Percentage (%) of fraction

Source

Kerosene Heavy fuel oil

J 13 30

K 4 44

02.3 Complete Figure 2.

You should:

• complete the y-axis scale

• plot the percentage of the heavy fuel oil fraction obtained from source K.

Use Table 4.

[2 marks]

Figure 2

02.4 Kerosene is in higher demand than heavy fuel oil.

Suggest why crude oil from source J is in higher demand than crude oil from

source K.

Use Table 4.

[1 mark]

Large hydrocarbon molecules can be cracked to produce smaller hydrocarbon

molecules including alkanes.

02.5 Which two of the following can be used to crack large hydrocarbon molecules?

[2 marks]

Tick ( ) two boxes.

A catalyst

A fertiliser

Air

Ozone

Steam

02.6 Alkanes have the general formula CnH2n+2

Complete the formula of the alkane molecule containing 11 carbon atoms.

[1 mark]

C1110H___

02.7 C2H6 is an alkane.

Which type of bond is found in a C2H6 molecule?

[1 mark]

Tick ( ) one box.

A double bond between two carbon atoms.

A double bond between two hydrogen atoms.

A single bond between two carbon atoms.

A single bond between two hydrogen atoms.

02.8 Which two substances are produced when alkanes completely combust?

[2 marks]

Tick ( ) two boxes.

Carbon

Carbon dioxide

Carbon monoxide

Hydrogen

Water

Mark scheme

Show the mark scheme Mark scheme for Question 2 with a total of 12 marks: 02.1 requires order C, B, A from top to bottom (1 mark); 02.2 requires 'higher' then 'lower' (2 marks); 02.3 requires the scale correctly labelled at intervals of 10 up to 40 or 50, and a bar for K plotted to 44% within tolerance (2 marks); 02.4 accepts 'contains more kerosene' or 'K contains less kerosene' (1 mark); 02.5 requires 'a catalyst' and 'steam' ticked (2 marks); 02.6 requires C11H24 (1 mark); 02.7 requires 'A single bond between two carbon atoms' ticked (1 mark); 02.8 requires 'Carbon dioxide' and 'Water' ticked (2 marks).

Question 2

AO /

Question Answers Extra information Mark

Spec. Ref.

02.1 must be in this order 1 AO3

C 4.7.1.2

B

A

AO /

Spec. Ref.

02.2 must be in this order AO2

higher 1 4.7.1.3

lower 1

AO /

Spec. Ref.

02.3 scale labelled at 20, 30, 40, (50) 1 AO2

% at 2 cm intervals 4.7.1.3

(K) bar drawn to 44% allow a tolerance of ± ½ a small 1

square

AO /

Spec. Ref.

02.4 contains more kerosene allow K contains less kerosene 1 AO3

4.7.1.3

4.7.1.4

AO /

Spec. Ref.

02.5 a catalyst 1 AO1

4.7.1.4

steam 1

AO /

Spec. Ref.

02.6 C11H24 1 AO2

4.7.1.1

AO /

Spec. Ref.

02.7 a single bond between two 1 AO1

carbon atoms 4.7.1.1

AO /

Spec. Ref.

02.8 carbon dioxide 1 AO1

4.7.1.3

water 1

Total Question 2 12

How to answer it

Crude Oil, Hydrocarbon Trends, Cracking & Combustion

📋 What This Question Tests

This question covers fundamental concepts from AQA Topic 7: Organic Chemistry:

  • Fractional distillation: temperature gradient and boiling point separation.
  • Trends in hydrocarbon properties (viscosity, flammability) related to molecular chain length.
  • Interpreting supply/demand data and graphing skills (completing scales and plotting bars).
  • Conditions required for cracking (catalytic and steam cracking).
  • The general formula of alkanes ( CnH2n+2 ) and alkane structure.
  • Products of the complete combustion of hydrocarbons.
Question 02.1 • 1 Mark

Separation in a Fractionating Column

Identifying where fractions condense based on boiling point

✅ Correct Answer

Order from top to bottom:

  • Top: C (Boiling point below 30 °C)
  • Middle: B (Boiling point 100–150 °C)
  • Bottom: A (Boiling point 200–300 °C)
[1 mark] Requires all three in the exact order: C, B, A.

💡 Key Knowledge

  • The column is hot at the bottom (400 °C) and cool at the top (30 °C).
  • Fractions with lower boiling points rise higher and condense near the top where it is cooler.
  • Fractions with higher boiling points condense near the bottom where temperatures remain high.

❌ Common Errors

  • Inverting the column: placing the highest boiling point (A) at the top.
  • Forgetting that gases with the weakest intermolecular forces leave at the very top.
Question 02.2 • 2 Marks

Properties and Chain Length of Hydrocarbons

Viscosity and flammability trends in alkanes

✅ Correct Answers

Compared to petrol, the viscosity of heavy fuel oil is higher. [1 mark]

Compared to petrol, the flammability of diesel oil is lower. [1 mark]

💡 Key Knowledge

  • Petrol: 5–12 carbons (shorter chains)
  • Diesel oil: 15–19 carbons (medium-long chains)
  • Heavy fuel oil: 20–40 carbons (very long chains)
  • Longer chains: have higher viscosity (thicker, flow less easily) and lower flammability (harder to ignite).

❌ Common Errors

  • Confusing viscosity with "runniness": higher viscosity means thicker/stickier, not more runny.
  • Thinking larger fuels catch fire more easily because they produce more heat. They actually have lower flammability because they vaporise less easily.
Question 02.3 • 2 Marks

Completing a Bar Chart and Axis Scale

Data presentation skills on graph paper

✅ Correct Answer & Actions

  1. Scale: Label the major grid lines (every 2 cm / 10 small squares) consistently as 20, 30, 40 (and optionally 50). [1 mark]
  2. Plotting Bar K: Draw a neat bar for source K with a height exactly at 44%. [1 mark]
Tolerance allowed: within ± ½ small square.

📐 Step-by-Step Plotting

  1. Check the existing scale: 0 to 10 covers 10 small squares (1 small square = 1%).
  2. Write labels at each major grid line: 20 at 20 squares, 30 at 30 squares, 40 at 40 squares.
  3. Locate 44 on the y-axis: count 4 small squares above the 40 line.
  4. Use a ruler and pencil to draw a bar matching the width of bar J.

🧠 Exam Technique

  • Always use a sharp pencil and a ruler for bars.
  • Double-check that your axis increments are linear and evenly spaced.
Question 02.4 • 1 Mark

Supply and Demand of Fractions

Interpreting crude oil composition data

✅ Correct Answer

Crude oil from source J contains more kerosene (13% compared to only 4% in K).

Also accepted: Source K contains less kerosene.

[1 mark] AO3 analysis.

🧠 Exam Technique

The question states: "Kerosene is in higher demand than heavy fuel oil. Suggest why crude oil from source J is in higher demand..."

  • Directly link the high-demand fraction (kerosene) to the source that has more of it.
  • Do not just write "it is better quality" without naming the fraction from the table.
Question 02.5 • 2 Marks

Methods of Cracking Hydrocarbons

Conditions for catalytic and thermal/steam cracking

✅ Correct Selections

Tick two boxes:

  • ☑ A catalyst [1 mark]
  • ☑ Steam [1 mark]

💡 Key Knowledge: The Two Cracking Types

  • Catalytic cracking: Vaporised hydrocarbons are passed over a hot catalyst (such as porcelain or aluminium oxide) at around 550 °C.
  • Steam cracking: Vaporised hydrocarbons are mixed with steam and heated to very high temperatures (over 800 °C).

❌ Common Errors

Ticking "Air" or "Ozone" — cracking is a thermal decomposition reaction, meaning it must take place without air/oxygen to prevent combustion.

Question 02.6 • 1 Mark

Alkane General Formula Calculation

Applying CnH2n+2

✅ Correct Answer

C11H24

Fill in the blank with 24.

[1 mark] AO2 calculation.

📐 Step-by-Step Calculation

  1. General formula for alkanes: CnH2n+2
  2. Here, the number of carbon atoms is n = 11 .
  3. Calculate hydrogens: (2 × 11) + 2 = 22 + 2 = 24 .
  4. Therefore, formula is C11H24 (undecane).

❌ Common Calculation Errors

  • Forgetting to add 2 (giving C11H22, which is an alkene).
  • Multiplying the +2 inside the brackets by mistake.
Question 02.7 • 1 Mark

Bonding in Ethane (C2H6)

Understanding saturated hydrocarbon structures

✅ Correct Selection

Tick (✓) one box:

  • ☑ A single bond between two carbon atoms. [1 mark]

💡 Key Knowledge

  • Alkanes are saturated hydrocarbons, meaning all bonds between carbon atoms are single covalent bonds ( C–C ).
  • Alkenes contain carbon-carbon double bonds ( C=C ).
  • Hydrogen can only form one covalent bond, so hydrogen-hydrogen double bonds are chemically impossible.

🧠 Diagram Visualisation

Ethane is drawn with two carbon atoms joined by a single line ( C–C ), with three hydrogen atoms bonded to each carbon atom ( C–H single bonds).

Question 02.8 • 2 Marks

Products of Complete Combustion

Oxidation of hydrocarbons in plentiful oxygen

✅ Correct Selections

Tick two boxes:

  • ☑ Carbon dioxide [1 mark]
  • ☑ Water [1 mark]

💡 Key Knowledge

Complete combustion occurs when hydrocarbons burn in plenty of oxygen:

hydrocarbon + oxygen → carbon dioxide + water

Both carbon and hydrogen are fully oxidised.

❌ Common Errors

  • Selecting carbon (soot) or carbon monoxide: these are produced during incomplete combustion (when oxygen is limited).
  • Selecting hydrogen: hydrogen oxidises to form water (H₂O), so pure hydrogen is never produced.

Topics

Chemistry · C7: Organic Chemistry

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.