Question

202(a) Give two examples of weak acids.

Answer 1

• The acids that do not dissociate completely into their ions in an aqueous solution are called weak acids.
• They undergo partial dissociation in an aqueous solution.
• An equilibrium will form between the concentration of the weak acid and its constituent ions.
• The examples of weak acid are:

(i) Acetic acid (CH₃COOH) is a weak acid because it dissociates partially into its constituent ions when dissolved in water. It is also known as ethanoic acid.

${\mathrm{CH}}_3\mathrm{COOH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{CH}}_3{\mathrm{COO}}^{{}^{-}}+{\mathrm{H}}_3{\mathrm{O}}^{+}$

(ii) Benzoic acid (C₆H₅COOH) is a weak acid as it undergoes partial dissociation in water. It is an aromatic carboxylic acid.

${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COO}}^{-}+{\mathrm{H}}_3{\mathrm{O}}^{+}$