A-LevelChemistryAtoms, molecules and stoichiometryFeb/Mar 2017Paper 3 Q212 Marks
You will carry out a second experiment to determine the concentration of hydrogen peroxide, FA 1, in moldm⁻³, by titration with acidified aqueous potassium manganate(VII). The equation for the reaction is given below. 2MnO₄⁻(aq) + 5H₂O₂(aq) + 6H⁺(aq) → 2Mn²⁺(aq) + 8H₂O(l) + 5O₂(g) FA 1 is a solution of hydrogen peroxide, H₂O₂. FA 3 is 0.0300 mol dm⁻³ potassium manganate(VII), KMnO₄. FA 4 is dilute sulfuric acid.
📋 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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