A-LevelChemistryEquilibriaFeb/Mar 2022Paper 1 Q121 Mark
Hydrogen and iodine react to form hydrogen iodide in an exothermic reaction. The equation is shown. H₂(g) + I₂(g) ⇌ 2HI(g) A 1 m³ reaction vessel contains H₂, I₂ and HI gases at equilibrium. The temperature is changed such that the total pressure in the 1 m³ vessel doubles. What is the effect on the value of Kp and on the position of equilibrium? [Figure 12.1]
Adecreases, moves left
Bincreases, moves right
Cno change, moves left
Dno change, no change
✓ Correct Answer
The correct answer is A: decreases, moves left
📋 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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