A-LevelChemistryElectrochemistryOct/Nov 2013Paper 1 Q161 Mark

Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 + 2HCl reaction 2 2KBr + 2H2SO4 → K2SO4 + SO2 + Br2 + 2H2O reaction 3 8KI + 5H2SO4 → 4K2SO4 + H2S + 4I2 + 4H2O What is the largest change in the oxidation number of sulfur in each of these reactions?

Q: What topic does this question test?

This question tests Electrochemistry in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

A0 (reaction 1), 0 (reaction 2), 4 (reaction 3)

B0 (reaction 1), 2 (reaction 2), 4 (reaction 3)

C0 (reaction 1), 2 (reaction 2), 8 (reaction 3)

D0 (reaction 1), 4 (reaction 2), 8 (reaction 3)

✓ Correct Answer

The correct answer is C: 0 (reaction 1), 2 (reaction 2), 8 (reaction 3)

📋 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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About This A-Level Chemistry Question

Topic

This multiple-choice question tests Electrochemistry in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Chemistry Oct/Nov 2013 examination, Paper 1 Variant 2.

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