A-LevelChemistryEquilibriaMay/June 2011Paper 1 Q51 Mark
Ammonia is manufactured on a large scale by the Haber process. In a particular plant, conditions of 400 °C and 250 atm in the presence of an iron catalyst are used. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH° = −92 kJ mol⁻¹ What could contribute most to increasing the equilibrium yield of ammonia?
Aadding more catalyst
Bincreasing the pressure to 400 atm
Cincreasing the temperature to 1000°C
Dusing air rather than nitrogen
✓ Correct Answer
The correct answer is B: increasing the pressure to 400 atm
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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