The diagram shows the process of adding calcium nitrate and strontium nitrate to separate boiling tubes and heating them. Identical conditions are used. [Figure showing two boiling tubes being heated, one with Ca(NO3)2 and universal indicator, the other with Sr(NO3)2 and universal indicator] As the reactions proceed, the water containing universal indicator changes colour. Which row describes the colour change and identifies the nitrate that causes the quickest colour change?
✓ Correct Answer
The correct answer is C: colour change of universal indicator: green to red, nitrate that causes the quickest colour change: Ca(NO₃)₂
📋 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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