A-LevelChemistryReaction kinetics9701/12 · May/June 2025 · Q91 Mark

Aqueous hydrogen peroxide, H2O2, decomposes into water and oxygen in the presence of a suitable catalyst. 50 cm³ of a 0.50 mol dm⁻³ solution of hydrogen peroxide produced 120 cm³ of oxygen in 2.0 minutes. The volume of gas was measured at room conditions. What is the average rate of decomposition of hydrogen peroxide during this 2.0 minute period?

A0.000083 mol dm⁻³ s⁻¹

B0.00083 mol dm⁻³ s⁻¹

C0.0017 mol dm⁻³ s⁻¹

D0.10 mol dm⁻³ s⁻¹

✓ Correct answer

C: 0.0017 mol dm⁻³ s⁻¹

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Topic: Reaction kinetics, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2025 Paper 1 Variant 2, question 9.

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