# Explain why a solution of sodium ethanoate (CH₃COONa) is basic, making reference to the relevant equilibrium and the relative strengths of the acid–base pairs involved.

> IB DP Chemistry Higher Level (2023 syllabus) — R3.1 Proton transfer reactions · Explain · 4 marks

## Mark scheme (4 marks)

1. Sodium ethanoate fully dissociates / ionises in water to give ethanoate ions (CH₃COO⁻) and Na⁺ ions.
2. Ethanoate ion acts as a Brønsted–Lowry base and accepts a proton from water: CH₃COO⁻ + H₂O ⇌ CH₃COOH + OH⁻
3. The equilibrium lies to the left / is only slightly displaced to the right because ethanoic acid is a weak acid.
4. The stronger base (CH₃COO⁻) dominates over the weaker base (OH⁻ / water acting as acid), so a small but net excess of OH⁻ is produced, making the solution basic (pH > 7).

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