A-LevelChemistryReaction kineticsMay/June 2025Paper 1 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?

Q: What is the correct answer to this A-Level Chemistry question?

The correct answer is C: 0.0017 mol dm⁻³ s⁻¹.

Q: What topic does this question test?

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

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

The correct answer is C: 0.0017 mol dm⁻³ s⁻¹

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

Source

This question appeared in the Cambridge A-Level Chemistry May/June 2025 examination, Paper 1 Variant 2.

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