Ethanoic acid is a carboxylic acid found in vinegar. Explain why ethanoic acid is described as a weak acid, and describe two chemical reactions that show it behaves as an acid.

Ethanoic acid is a weak acid because it only partially dissociates in water:
1.
CH₃COOH ⇌ CH₃COO⁻ + H⁺
Only a small fraction of the molecules ionise, so the concentration of H⁺ is low.

Two reactions that show its acidic behaviour:
2. With a metal such as magnesium:
2Mg + 2CH₃COOH → 2CH₃COO⁻Mg²⁺ + H₂↑
The acid donates H⁺ to the metal, forming a metal ethanoate salt and hydrogen gas.

3. With a carbonate (e.g. Na₂CO₃):
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑
The acid neutralises the carbonate, giving sodium ethanoate, water and carbon dioxide.

Both reactions involve the donation of H⁺ ions, demonstrating ethanoic acid’s behaviour as an acid.