A-LevelChemistryAnalytical techniquesFeb/Mar 2022Paper 5 Q19 Marks
A student has a sample of copper(II) sulfate crystals, CuSO₄•xH₂O. The student wants to show that the value of x is 5. The student uses the following method. step 1 Weigh a clean crucible on a balance reading to two decimal places. Record the mass. step 2 Place the sample of CuSO₄•xH₂O into the crucible. Record the mass. step 3 Heat the crucible gently for about 1 minute then strongly for about 4 minutes. step 4 Weigh the crucible and contents. Record the mass.
📋 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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