AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2024: Question 9
8 marks · Standard Demand difficulty · Short Answer
Explain the Haber process recycling, identify the catalyst, describe the test for oxygen, complete a reaction profile, and state a use for ammonium nitrate.
Practise this questionQuestion
Question text
09 This question is about ammonia and nitric acid.
In the Haber process ammonia is produced from nitrogen and hydrogen.
Figure 10 represents the Haber process.
Figure 10
09.1 Pipe P links the condenser to the reactor.
Why is the condenser linked to the reactor?
Use Figure 10.
[1 mark]
09.2 Which metal is used as a catalyst in this reaction?
[1 mark]
Nitric acid is produced by reacting ammonia with oxygen.
The word equation for the production of nitric acid is:
ammonia + oxygen → water + nitric acid
*35* Platinum is a catalyst in this reaction.
09.3 Describe the test for oxygen gas.
Give the result if oxygen gas is present.
[2 marks]
Test
Result
Figure 11 represents the reaction profile of the catalysed reaction between ammonia
and oxygen.
Figure 11
09.4 Complete the reaction profile for the catalysed reaction in Figure 11.
You should:
• label the activation energy
• label the reactants and products, using the names of the reactants and products.
[2 marks]
09.5 How would Figure 11 be different if no catalyst was used?
[1 mark]
Tick ( ) one box.
The final energy level would be higher.
The final energy level would be lower.
The line would reach a higher peak.
The line would reach a lower peak.
09.6 Ammonia and nitric acid react to produce the salt, ammonium nitrate.
Ammonium ions and nitrate ions both contain nitrogen.
Suggest one use of ammonium nitrate.
[1 mark]
Mark scheme
Show the mark scheme
Question 9
AO /
Question Answers Extra information Mark
Spec. Ref.
09.1 to recycle (remaining) nitrogen allow to recycle unreacted 1 AO1
and hydrogen gases 4.10.4.1
allow to return nitrogen and
hydrogen to the reactor
AO /
Spec. Ref.
09.2 iron allow Fe 1 AO1
4.6.1.4
4.10.4.1
AO /
Spec. Ref.
09.3 (test) AO1
glowing splint 1 4.8.2.2
(result)
(splint) relights MP2 is dependent upon MP1– – 1 –
being awarded
AO /
Spec. Ref.
09.4 labelled vertical arrow from ignore arrow heads 1 AO2
dotted line to peak 4.6.1.4
4.10.4.1
ammonia and oxygen on left allow NH3 for ammonia 1 4.10.4.2
and allow O2 for oxygen
nitric acid and water on right allow HNO3 for nitric acid
allow H2O for water
an answer of
scores 2 marks
AO /
Spec. Ref.
09.5 the line would reach a higher 1 AO1
peak 4.6.1.4
4.10.4.1
4.10.4.2
AO /
Spec. Ref.
09.6 fertilisers allow explosives 1 AO3
allow sports injury packs 4.10.4.1
4.10.4.2
Total Question 9 8
How to answer it
Ammonia, Nitric Acid & Reaction Profiles
This question assesses fundamental industrial chemistry and energetics from AQA Chemistry:
- Haber Process Conditions & Flow Scheme: Identifying industrial recycling loops and industrial catalysts.
- Qualitative Gas Tests: Recalling standard laboratory tests and observations for oxygen.
- Exothermic Reaction Profiles: Correctly labelling activation energy ( E ₐ) and chemical species from word equations.
- Catalyst Action: Predicting changes to reaction profiles when catalysts are omitted.
- Fertiliser Uses: Identifying essential agricultural applications of ammonium salts.
Purpose of Pipe P in the Haber Process
AO1 • Specification Reference: 4.10.4.1
✅ Correct Answer
To recycle (unreacted) nitrogen and hydrogen back into the reactor.
🧠 Exam Technique
Trace the flow lines in Figure 10: gases leave the condenser from the top and lead directly back into the reactor. Ammonia condenses as a liquid at the bottom, leaving nitrogen and hydrogen as gases to be returned.
❌ Common Errors
- Saying "to release excess pressure" or "to let heat escape".
- Writing "to recycle ammonia" (ammonia is removed as a liquid at the base, not piped back).
Catalyst in the Haber Process
AO1 • Specification Reference: 4.6.1.4, 4.10.4.1
✅ Correct Answer
Iron (or chemical symbol Fe ).
💡 Key Knowledge
The Haber process operates at roughly 450 °C, 200 atmospheres, over an iron catalyst. This is a core recall fact for AQA GCSE Chemistry.
❌ Common Errors
Confusing iron with platinum (which the question mentions immediately afterwards for nitric acid production) or nickel (used in the hydrogenation of vegetable oils).
Gas Test for Oxygen
AO1 • Specification Reference: 4.8.2.2
✅ Correct Answer
- Test: Insert a glowing splint [1 mark]
- Result: The splint relights [1 mark]
🧠 Mark Scheme Dependency
Mark Point 2 is strictly dependent on Mark Point 1. If you write "burning splint", you get 0 marks for the test and automatically cannot earn the mark for "relights".
❌ Common Gas Test Confusions
- Hydrogen: Burning/lit splint → squeaky pop.
- Oxygen: Glowing splint → relights.
- Carbon dioxide: Limewater → turns cloudy.
- Chlorine: Damp litmus paper → bleaches white.
Completing an Exothermic Reaction Profile
AO2 • Specification Reference: 4.6.1.4, 4.10.4.1, 4.10.4.2
✅ Correct Answer & Requirements
- Activation Energy (1 mark): A vertical arrow pointing from the dotted line (reactants level) up to the peak of the curve.
- Labels (1 mark): "Ammonia + oxygen" (or NH₃ + O₂) on the reactant line (left) AND "Nitric acid + water" (or HNO₃ + H₂O) on the product line (right).
❌ Where Students Lost Marks
- Writing generic names: Writing "reactants" and "products" instead of the actual chemical names provided in the prompt.
- Arrow drawn incorrectly: Drawing the arrow all the way from the horizontal x-axis or from the product line to the peak.
- Missing one substance: E.g. writing just "nitric acid" on the right while omitting "water".
- Left plateau (higher): Label clearly as ammonia + oxygen .
- Right plateau (lower): Label clearly as nitric acid + water .
- Activation Energy ( E ₐ): Draw a single- or double-headed vertical arrow starting exactly at the level of the horizontal dotted line (reactants level) and reaching the apex of the peak. Label it activation energy (or Eₐ ).
Effect of Catalyst on Reaction Profile
AO1 • Specification Reference: 4.6.1.4
✅ Correct Answer
The line would reach a higher peak. (Box 3 ticked)
💡 Why This Happens
A catalyst provides an alternative reaction pathway with a lower activation energy. Therefore, if no catalyst is used, the activation energy is higher — meaning the energy curve must climb to a higher peak.
❌ Common Misconception
Thinking catalysts change the starting or final energy levels. Catalysts do not alter overall energy change (ΔH). Reactants and products stay at the exact same energy levels.
Use of Ammonium Nitrate
AO3 • Specification Reference: 4.10.4.1, 4.10.4.2
✅ Correct Answer
Fertilisers (or fertiliser production).
💡 Why Nitrogen Matters
Plants require nitrogen to synthesise proteins and grow. Ammonium nitrate ( NH₄NO₃ ) contains two sources of nitrogen (ammonium ions NH₄⁺ and nitrate ions NO₃⁻ ), making it an exceptionally rich NPK fertiliser ingredient.
🧠 Alternative Allowed Answers
- Explosives (industrial blasting agent).
- Sports injury packs / cold packs (dissolving ammonium nitrate in water is endothermic).
Topics
Chemistry · C5: Energy Changes · C6: The Rate and Extent of Chemical Change · C8: Chemical Analysis · C10: Using Resources
Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.