A-LevelChemistryElectrochemistryOct/Nov 2021Paper 4 Q39 Marks
Pure water is a very poor conductor of electricity. However, when hydrogen chloride gas is dissolved in water, ions are formed and a current flows during electrolysis. HCl(g) + aq → H⁺(aq) + Cl⁻(aq) The overall change after electrolysis is that hydrogen chloride gas is converted into hydrogen and chlorine. 2HCl(g) → H₂(g) + Cl₂(g) When a current of 3.10A is passed through the solution for Y minutes, 351 cm³ of chlorine are produced at the anode, measured under room conditions.
📋 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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