Only is hydrolysing and acid dissociation constant of in water is . — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The concentration of $\text{SO}_4^{2-}$ is $2 \times 0.25 = 0.50\text{ M}$ because 1 formula unit provides 2 sulphate ions. The base hydrolysis constant $K_h = K_w / K_a = 10^{-14} / (1.25 \times 10^{-2}) = 8 \times 10^{-13}$. $[\text{OH}^-] = \sqrt{K_h \cdot C} = \sqrt{8 \times 10^{-13} \times 0.50} = \sqrt{4 \times 10^{-13}} \approx 6.32 \times 10^{-7}\text{ M}$. From this, $[\text{H}_3\text{O}^+] = 10^{-14} / (6.32 \times 10^{-7}) = 1.58 \times 10^{-8}\text{ M}$. Therefore, correct answer is D.