AQA GCSE Combined Science: Trilogy Chemistry Paper 2 (Higher), June 2025: Question 4

15 marks · Standard Demand difficulty · Short Answer

Analyze the production of methanol from carbon monoxide and hydrogen, focusing on formulations, dynamic equilibrium, reaction conditions, catalysts, and balancing chemical equations.

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Question

Question text

04 This question is about methanol.

04.1 Methanol is used in screenwash.

Screenwash is used to keep car windscreens clean.

Screenwash is a formulation.

Define the term ‘formulation’.

[1 mark]

Carbon monoxide and hydrogen are used to produce methanol.

The conditions used in the production of methanol are:

• high temperature

• high pressure

• a catalyst.

The equation for the reaction is:

CO(g) + 2H2(g) ⇌ CH3OH(g)

91 kJ/mol of energy is transferred during the exothermic forward reaction.

04.2 How much energy is transferred when methanol is decomposed into carbon monoxide

and hydrogen?

[1 mark]

Tick ( ) one box.

< 91 kJ/mol

91 kJ/mol

> 91 kJ/mol

04.3 A scientist developed a principle to predict the effect of changing conditions on a

system at equilibrium.

What was the name of the scientist?

[1 mark]

04.4 What is the effect of increasing the temperature on the proportion of methanol in the

equilibrium mixture?

[1 mark]

Tick ( ) one box.

The proportion of methanol decreases.

The proportion of methanol stays the same.

The proportion of methanol increases.

04.5 What is the effect of using a catalyst on the proportion of methanol in the

equilibrium mixture?

[1 mark]

Tick ( ) one box.

The proportion of methanol decreases.

The proportion of methanol stays the same.

The proportion of methanol increases.

04.6 Explain the effect of increasing the pressure on the proportion of methanol in the

equilibrium mixture.

[3 marks]

04.7 Explain the effect of using a catalyst on the rate of production of methanol.

*15* [3 marks]

04.8 The catalyst allows the reaction to take place at a lower temperature.

Explain one advantage of using a lower temperature in the production of methanol.

Do not refer to the position of equilibrium in your answer.

[2 marks]

04.9 Methanol (CH3OH) can also be produced by reacting carbon dioxide with hydrogen.

Water is the other product of the reaction.

Write a balanced equation for the reaction.

[2 marks]

+ → +

Mark scheme

Show the mark scheme

Question 4

AO /

Question Answers Extra information Mark

Spec. Ref.

04.1 a mixture that has been 1 AO1

designed as a useful product 5.8.1.2

AO /

Spec. Ref.

04.2 91 kJ/mol 1 AO2

5.6.2.2

AO /

Spec. Ref.

04.3 Le Chatelier 1 AO1

5.6.2.4

AO /

Spec. Ref.

04.4 the proportion of methanol 1 AO2

decreases 5.6.2.4

5.6.2.6

AO /

Spec. Ref.

04.5 the proportion of methanol stays 1 AO3

the same 5.6.1.4

– – – 5.6.2.4

AO /

Spec. Ref.

04.6 (increasing the pressure) 1 AO2

increases the proportion of 5.6.2.4

methanol 5.6.2.7

(because) there are more 1

molecules / moles of reactant

(than product)

(so) the equilibrium (position) 1

shifts to the side with fewer

molecules / moles 15

AO /

Spec. Ref.

04.7 (the catalyst) increases the rate 1 AO1

of the reaction 5.6.1.4

(by) providing an alternative 1

pathway (for the reaction)

(with) a lower activation energy 1

AO /

Spec. Ref.

04.8 reduces the costs 1 AO2

5.6.1.4

5.9.2.2

(because) less energy is used 1 5.9.2.4

less fuels burned (1)

(so) less contribution to global allow (so) less carbon dioxide

warming (1) – producedSCIENCE: TRILOGY – –

AO /

Spec. Ref.

16 04.9 CO2 + 3 H2 → CH3OH + H2O allow multiples 2 AO2

5.3.1.1

allow 1 mark for

CO2 + H2 → CH3OH + H2O

with no / incorrect balancing

numbers

Total Question 4 15

How to answer it

AQA GCSE Combined Science: Trilogy

Methanol Production: Reversible Reactions & Equilibria

Complete Question Walkthrough, Model Answers & Examiner Strategies

What this question tests

This 15-mark structured question spans key areas from Organic Formulations, Chemical Energy Changes, Rates of Reaction, and Le Chatelier’s Principle:

Formulations: Stating the precise specification definition for a commercial mixture.
Conservation of Energy: Understanding energy transfer in reversible chemical reactions.
Le Chatelier's Principle: Predicting and explaining the impact of temperature, pressure, and catalysts on position of equilibrium and yield.
Collision Theory & Catalysts: Explaining activation energy and reaction pathways.
Industrial Trade-offs: Evaluating cost and environmental factors in industrial chemical processes.
Symbol Equations: Writing and balancing equations involving organic molecules.

Reaction Information Given in Exam:
CO(g) + 2H₂(g) ⇌ CH₃OH(g)
"91 kJ/mol of energy is transferred during the exothermic forward reaction."

Question 04.1 • 1 Mark

Definition of a Formulation

✅ Correct Answer 1 mark

A mixture that has been designed as a useful product.

🧠 Exam Technique

This is a standard recall definition from Topic 8 (Chemical Analysis). You must use the word mixture and mention it is designed/made as a useful product.

❌ Common Errors

Students often lose this mark by writing vague answers like "a liquid used for cleaning" or confusing a formulation with a pure substance or a chemical compound.

Question 04.2 • 1 Mark

Energy Transfer in Reversible Reactions

✅ Correct Answer 1 mark

Tick: 91 kJ/mol (middle box)

💡 Key Knowledge

Conservation of Energy: The amount of energy released by the forward exothermic reaction is exactly equal to the amount of energy absorbed by the reverse endothermic reaction.

Question 04.3 • 1 Mark

Naming the Equilibrium Scientist

✅ Correct Answer 1 mark

Le Chatelier (or Le Chatelier's Principle)

🧠 Exam Technique

Phonetic spellings are usually accepted if unambiguous, but aim for accurate recall: Henri Le Chatelier.

Question 04.4 • 1 Mark

Effect of Increasing Temperature on Yield

✅ Correct Answer 1 mark

Tick: The proportion of methanol decreases.

💡 Key Knowledge

The forward reaction is exothermic (gives out heat). If you raise the temperature, the system acts to counteract the change by shifting in the endothermic direction (backward), decreasing the proportion of methanol at equilibrium.

Question 04.5 • 1 Mark

Effect of a Catalyst on Equilibrium Composition

✅ Correct Answer 1 mark

Tick: The proportion of methanol stays the same.

❌ Common Error Alert

Many students incorrectly tick "increases". Remember: A catalyst increases the rate of both forward and reverse reactions equally. It has no effect on the position of equilibrium or the percentage yield!

Question 04.6 • 3 Marks

Explaining the Effect of Pressure on Equilibrium

✅ Model Answer 3 marks

Increasing the pressure increases the proportion of methanol. 1 mark
Because there are more molecules / moles of gas on the reactant side (3 moles) than on the product side (1 mole). 1 mark
So the equilibrium position shifts to the side with fewer molecules / moles. 1 mark

📐 Counting Gas Moles

CO(g) + 2H₂(g) ⇌ CH₃OH(g)

Left side (reactants): 1 + 2 = 3 moles of gas
Right side (products): 1 mole of gas

Increasing pressure pushes equilibrium toward the side with fewer moles to reduce pressure.

Question 04.7 • 3 Marks

Explaining How a Catalyst Affects Reaction Rate

✅ Model Answer 3 marks

The catalyst increases the rate of production / reaction. 1 mark
By providing an alternative reaction pathway... 1 mark
...which has a lower activation energy. 1 mark

🧠 Examiner Insight

This is a classic 3-mark question. Top students hit all three marking points like a checklist: (1) Rate increases → (2) Alternative pathway → (3) Lower activation energy.

Question 04.8 • 2 Marks

Advantage of Using a Lower Temperature (Industrial Context)

⚠️ Question Restriction

The prompt explicitly says: "Do not refer to the position of equilibrium in your answer." Any mention of yield, equilibrium shifting, or Le Chatelier gets 0 marks!

✅ Route 1: Cost & Energy 2 marks

Reduces costs 1 mark
Because less energy is required/used 1 mark

✅ Route 2: Environmental 2 marks

Less fossil fuels burned 1 mark
So less carbon dioxide produced / less contribution to global warming 1 mark

Question 04.9 • 2 Marks

Writing and Balancing the Chemical Equation

📐 Step-by-Step Balancing

Step 1: Write correct formulas for reactants and products
Reactants: Carbon dioxide (CO₂) and Hydrogen (H₂)
Products: Methanol (CH₃OH) and Water (H₂O)
CO₂ + H₂ → CH₃OH + H₂O 1 mark for all correct formulas

Step 2: Balance the atoms on each side

Carbon (C): 1 on left, 1 on right — Balanced
Oxygen (O): 2 on left (in CO₂), 2 on right (1 in CH₃OH + 1 in H₂O) — Balanced
Hydrogen (H): 2 on left (in H₂), but 4 + 2 = 6 on right (4 in CH₃OH, 2 in H₂O) — Not balanced

Place a coefficient of 3 in front of H₂ to get 6 hydrogen atoms on the left: 3 × 2 = 6.

✅ Final Balanced Equation 2 marks

CO₂ + 3H₂ → CH₃OH + H₂O

(Multiples such as 2CO₂ + 6H₂ → 2CH₃OH + 2H₂O are also accepted)

Topics

Chemistry · C3: Quantitative Chemistry · C6: The Rate and Extent of Chemical Change · C8: Chemical Analysis

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 2 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.