A-LevelChemistryChemical energetics9701/12 · May/June 2025 · Q131 Mark

Under certain conditions, CCl4 and H2O react as shown. The activation energy for the reaction is +62 kJ mol⁻¹. CCl4 + 2H2O → CO2 + 4HCl ΔH = −61.5 kJ mol⁻¹ Which enthalpy profile diagram best fits this reaction?

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ADiagram showing an exothermic reaction profile with the activation energy barrier above the reactants.

BDiagram showing an endothermic reaction profile with the activation energy barrier above the reactants.

CDiagram showing an exothermic reaction profile with a larger activation energy barrier above the reactants than option A.

DDiagram showing an endothermic reaction profile with the activation energy barrier above the reactants.

✓ Correct answer

D: Diagram showing an endothermic reaction profile with the activation energy barrier above the reactants.

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Topic: Chemical energetics, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2025 Paper 1 Variant 2, question 13.

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