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Chemistry · Ch 3 — Ionic Equilibria

Ionisation of acids and bases

3.4

Ionisation of acids and bases

Acids and bases are classified as strong acids and strong bases, weak acids and weak bases on the basis of their extent of dissociation. Strong acids and bases are almost completely dissociated in water. For example :

HCl(aq)→H+(aq)+Cl−(aq)\mathrm{HCl(aq)} \rightarrow \mathrm{H^{+}(aq)} + \mathrm{Cl^{-}(aq)}

NaOH(aq)→Na+(aq)+OH−(aq)\mathrm{NaOH(aq)} \rightarrow \mathrm{Na^{+}(aq)} + \mathrm{OH^{-}(aq)}

Typical strong acids are HCl, HNO3\mathrm{HNO_3}, H2SO4\mathrm{H_2SO_4}, HBr and HI while typical strong bases may include NaOH and KOH.

Weak acids and weak bases are partially dissociated in water. The solution of a weak acid or a weak base contains undissociated molecules along with a small number of ions at equilibrium. For example :

CH3COOH(aq)⇌CH3COO−(aq)+H+(aq)\mathrm{CH_3COOH(aq)} \rightleftharpoons \mathrm{CH_3COO^{-}(aq)} + \mathrm{H^{+}(aq)} …

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