A-LevelChemistryChemical energeticsMay/June 2024Paper 3 Q210 Marks
2 A sample of ammonium bromide has been accidentally mixed with another salt. A student suggests that the percentage purity of the ammonium bromide can be determined by measuring the change in temperature when a solution is prepared. The enthalpy change when the sample dissolves in water, ΔH, can then be calculated and compared with the literature value for ammonium bromide. You will carry out the student's experiment. FA 4 is ammonium bromide, NH4Br, mixed with another salt.
📋 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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