A-LevelChemistryGroup 179701/12 · May/June 2025 · Q201 Mark

Sodium bromide is warmed with concentrated sulfuric acid. Which row describes the change in the oxidation number of the sulfur and the role of the bromide ions in the reaction?

A[change in oxidation number of sulfur: +6 to +4, role of bromide ions: oxidising agent]

B[change in oxidation number of sulfur: +6 to +4, role of bromide ions: reducing agent]

C[change in oxidation number of sulfur: +4 to 0, role of bromide ions: oxidising agent]

D[change in oxidation number of sulfur: +4 to 0, role of bromide ions: reducing agent]

✓ Correct answer

B: [change in oxidation number of sulfur: +6 to +4, role of bromide ions: reducing agent]

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Topic: Group 17, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2025 Paper 1 Variant 2, question 20.

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