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A-LevelChemistryChemical energeticsFeb/Mar 2022Paper 1 Q91 Mark

Nitrogen monoxide is an atmospheric pollutant that is formed inside car engines by an endothermic reaction between nitrogen and oxygen. N₂(g) + O₂(g) → 2NO(g) Which diagram correctly represents the energy profile for this reaction? [Figure 9.1]

ADiagram showing an endothermic reaction profile with products at higher energy than reactants, and activation energy Ea.
BDiagram showing an exothermic reaction profile with products at lower energy than reactants.
CDiagram showing an endothermic reaction profile with products at higher energy than reactants, but ΔH shown incorrectly as negative.
DDiagram showing an exothermic reaction profile with products at lower energy than reactants, but activation energy shown incorrectly.

✓ Correct Answer

The correct answer is A: Diagram showing an endothermic reaction profile with products at higher energy than reactants, and activation energy Ea.

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

Source

This question appeared in the Cambridge A-Level Chemistry Feb/Mar 2022 examination, Paper 1 Variant 2.

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