A-LevelChemistryElectrochemistry9701/12 · May/June 2023 · Q111 Mark

LiAlH₄ contains AlH₄⁻ ions in which aluminium has an oxidation state of +3. LiAlH₄ reacts with water, as shown. LiAlH₄ + 4H₂O → 4H₂ + LiOH + Al(OH)₃ In this reaction, each of the four water molecules produces one hydroxide ion. It does this by losing one H⁺ ion, which reacts with the LiAlH₄. Which changes in oxidation number occur in this reaction?

AAl increases by 1 and H decreases by 1.

BH decreases by 2 and also increases by 1.

CH increases by 1 and also decreases by 1.

DO decreases by 1 and H increases by 1.

✓ Correct answer

C: H increases by 1 and also decreases by 1.

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Topic: Electrochemistry, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2023 Paper 1 Variant 2, question 11.

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