A-LevelChemistryAnalytical techniquesOct/Nov 2025Paper 3 Q210 Marks
Hydrated zinc sulfate has the formula ZnSO4•yH2O where y is an integer. Hydrated zinc sulfate decomposes when heated, losing only its water of crystallisation and becoming anhydrous. You will determine the value of y in ZnSO4•yH2O by heating the hydrated salt until it becomes anhydrous. FA 4 is hydrated zinc sulfate, ZnSO4•yH2O.
📋 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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