A solution of ammonia () has a pH of 11.5. Find the molarity of the solution given . — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

$pH = 11.5 \implies pOH = 2.5 \implies [OH^-] = 10^{-2.5} \approx 3.16 \times 10^{-3} \text{ M}$. For a weak base, $[OH^-] = \sqrt{K_b C} \implies C = [OH^-]^2 / K_b = 10^{-5} / (1.8 \times 10^{-5}) \approx 0.55 \text{ M}$.