A-LevelChemistryAtoms, molecules and stoichiometryOct/Nov 2025Paper 1 Q31 Mark
The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of the products. The two relevant redox equations are shown. H2S(aq) S(s) + 2H+(aq) + 2e¯ SO2(aq) + 4H+(aq) + 4e¯ ⇌ S(s) + 2H2O(I) How many moles of hydrogen sulfide are needed to react with sulfur dioxide to produce 1 mol of sulfur?
A1 mol
B2 mol
C3 mol
D2 mol
✓ Correct Answer
The correct answer is B: 2 mol
📋 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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