O-LevelChemistryAcids, Bases & Salts5070/11 · May/June 2025 · Q201 Mark

The pH of dilute ethanoic acid is measured. The equation for the partial dissociation of ethanoic acid is shown. CH3COOH(aq) ⇌ CH3COO¯(aq) + H+(aq) Aqueous sodium ethanoate, CH3COONa, is added to the dilute ethanoic acid and the pH is measured again. What is the initial pH of the dilute ethanoic acid and how does it change after the addition of the aqueous sodium ethanoate?

A3–4 | increases

B3–4 | decreases

C8–9 | increases

D8–9 | decreases

✓ Correct answer

A: 3–4 | increases

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Topic: Acids, Bases & Salts, O-Level Chemistry (syllabus 5070). Multiple choice, 1 mark.
Source: O-Level Chemistry, May/June 2025 Paper 1 Variant 1, question 20.

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