A-LevelChemistryAtoms, molecules and stoichiometryFeb/Mar 2017Paper 3 Q111 Marks
The concentration of hydrogen peroxide may be given in moldm-³ or as 'volume strength'. You will determine the concentration of hydrogen peroxide in moldm-³ and in 'volume strength' by a gas collection method. Hydrogen peroxide decomposes to form water and oxygen. The reaction is much faster in the presence of a catalyst such as manganese(IV) oxide. 2H2O2(aq) → 2H2O(l) + O2(g) 'Volume strength' is defined as the volume of oxygen in cm³ produced from the decomposition of 1.0 cm³ of hydrogen peroxide at room temperature and pressure. For example, 1.0cm³ of '100 volume' hydrogen peroxide will produce 100 cm³ of oxygen. FA 1 is a solution of hydrogen peroxide, H2O2. FA 2 is manganese(IV) oxide, MnO2.
📋 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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