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Edexcel A-Level Chemistry A2 16.1 The Terms Oxidation and Reduction in Terms of Electron Transfer and Changes in Oxidation Number Applied to S P Questions

Track the element that changes oxidation number, then state whether electrons are gained or lost and use that change to justify the redox decision.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Use oxidation-number changes to justify whether a reaction is redox or not.
  • Link reduction to electron gain and a decrease in oxidation number in MCQ contexts.
  • Identify which species is oxidised or reduced from balanced equations or half-cells.

Edexcel A-Level Chemistry A2 16.1 The Terms Oxidation and Reduction in Terms of Electron Transfer and Changes in Oxidation Number Applied to S P Questions question 1

[Maximum number: 2]

This question is about mercury, Hg, and its compounds.
Mercury is a liquid element in the same group of the Periodic Table as zinc.
The electronic configuration of mercury is [Xe]4f145 d106 s2[\mathrm{Xe}] 4 \mathrm{f}^{14} 5 \mathrm{~d}^{10} 6 \mathrm{~s}^{2}.

Mercury reacts with nitric acid to form an aqueous solution of Hg(NO3)2\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2} and nitrogen monoxide gas.

The unbalanced equation is shown.

Hg(l)+HNO3(aq)→Hg(NO3)2(aq)+NO( g)+H2O(l)\mathrm{Hg}(\mathrm{l})+\mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow \mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{NO}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Explain, using oxidation numbers, why this is a redox reaction.
(2)

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