The pH of a 0.1 molar solution of a weak monoprotic acid HQ is 3. The value of the ionization consta — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

pH = 3 implies $[H^+] = 10^{-3} \text{ M}$. For a weak acid, $[H^+] \approx \sqrt{K_a C}$. So, $K_a = \frac{[H^+]^2}{C} = \frac{(10^{-3})^2}{0.1} = \frac{10^{-6}}{10^{-1}} = 10^{-5}$.