A-LevelChemistryCarbonyl compoundsMay/June 2023Paper 1 Q351 Mark

The mechanism for the reaction between ethanal and hydrogen cyanide starts with the step shown. [Figure of reaction mechanism, step 1] What is the correct structure of the intermediate ion formed, and what is the next step in this mechanism?

Q: What topic does this question test?

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

ADiagram showing the intermediate ion H₂C(CN)O⁻ and its protonation by H⁺

BDiagram showing the intermediate ion H₂C(CN)O⁻ with an incorrect subsequent reaction arrow

CDiagram showing the intermediate ion H₂C(CN)O⁻ with an incorrect subsequent reaction arrow

DDiagram showing the intermediate ion H₂C(CN)O⁻ and its protonation by H⁺

✓ Correct Answer

The correct answer is D: Diagram showing the intermediate ion H₂C(CN)O⁻ and its protonation by H⁺

📋 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 Carbonyl compounds in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Chemistry May/June 2023 examination, Paper 1 Variant 2.

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