A-LevelChemistryElectrochemistryOct/Nov 2016Paper 1 Q311 Mark
Photochromic lenses in spectacles darken in sunlight because silver crystals are produced by the reaction shown. Ag⁺ + Cl⁻ → Ag + Cl Which statements are correct for this reaction? 1 Both silver and chlorine atoms have an oxidation number of zero. 2 The oxidation number of chlorine increases. 3 Electrons are transferred from Cl⁻ ions to Ag⁺ ions.
A1, 2 and 3 are correct
B1 and 2 only are correct
C2 and 3 only are correct
D1 only is correct
✓ Correct Answer
The correct answer is A: 1, 2 and 3 are correct
📋 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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