A-LevelChemistryGroup 17May/June 2017Paper 1 Q171 Mark
A powder is known to be either a single sodium halide or a mixture of two sodium halides. A sample of the powder was dissolved in water. Aqueous silver nitrate was added, and a pale yellow precipitate was formed. When concentrated aqueous ammonia was then added, this precipitate partly dissolved leaving a darker yellow precipitate. What might the powder be?
Asodium bromide only
Bsodium iodide only
Cmixture of sodium chloride and sodium bromide
Dmixture of sodium chloride and sodium iodide
✓ Correct Answer
The correct answer is D: mixture of sodium chloride and sodium iodide
📋 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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