The decomposition of hydrogen peroxide in the presence of MnO2 produces water and oxygen gas. 2H2O2(aq) → 2H2O(l) + O2(g) The volume of gas collected when 0.2g of MnO2 is added to two different hydrogen peroxide solutions at 20 °C is shown on the graph as curves X and Y. [Figure of graph with volume of gas vs time showing curves X and Y] Which row shows the conditions that will result in curves X and Y?
✓ Correct Answer
The correct answer is C: curve X: volume of H2O2/cm³ 50, concentration of H2O2/mol dm⁻³ 0.1, form of MnO2 lumps; curve Y: volume of H2O2/cm³ 20, concentration of H2O2/mol dm⁻³ 0.2, form of MnO2 powder
📋 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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