A-LevelChemistryChemical energetics9701/12 · May/June 2017 · Q71 Mark

In the high temperatures of car engines, nitrogen reacts with oxygen to give nitrogen monoxide. ½N₂(g) + ½O₂(g) → NO(g) ΔH° = +90 kJ mol⁻¹ This reaction has activation energy Ea. Which reaction pathway diagram could correctly represent this reaction?

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AEnergy profile for an exothermic reaction where products are at a lower energy level than reactants, showing Ea and negative ΔH°.

BEnergy profile for an exothermic reaction where products are at a lower energy level than reactants, showing Ea and negative ΔH°.

CEnergy profile for an endothermic reaction where products are at a higher energy level than reactants, showing Ea and positive ΔH°.

DEnergy profile for an endothermic reaction where products are at a higher energy level than reactants, showing Ea and positive ΔH°.

✓ Correct answer

C: Energy profile for an endothermic reaction where products are at a higher energy level than reactants, showing Ea and positive ΔH°.

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Topic: Chemical energetics, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2017 Paper 1 Variant 2, question 7.

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