Calculating the pH of a Strong Base

The strength of a base is its ability to dissociate and generate OH^- ions in solution. Strong bases are alkalis. They dissociate completely to give hydroxide ions and cations. For example, sodium hydroxide is a strong base.NaOH(aq) → Na⁺(aq) + OH^-(aq)Since pH = -log₁₀[H⁺] we need to know the hydrogen ion concentration in order to find the pH. We can use the fact that K_w = [H⁺] [OH^-] = 1.0 x 10^-14 at 25°C to find the hydrogen ion concentration.For a 0.2 moldm^-3 solution of NaOH, the [H⁺] = K_w/ [OH^-] and [H⁺] = 1 x 10^-14/ 0.2pH = -log₁₀ (1 x 10^-14/ 0.2) = 13.3