Both, and are hydrolysing. — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

When both ions hydrolyse, $\text{Al}^{3+}$ produces $\text{H}^+$ and $\text{SO}_4^{2-}$ consumes it. Let the actual $[\text{H}^+] = h$. The hydrolysis of $\text{Al}^{3+}$ creates $h$ and also converts some $\text{SO}_4^{2-}$ to $\text{HSO}_4^-$. Setting up the coupled equilibria $1.4 \times 10^{-5} = \frac{x \cdot h}{0.25 - x}$ and $1.25 \times 10^{-2} = \frac{h(0.50)}{y}$ (where $y$ is $[\text{HSO}_4^-]$) and using charge balance, the mathematical evaluation yields $h \approx 2.93 \times 10^{-4}\text{ M}$. Therefore, correct answer is A.