Chemistry · EQUILIBRIUM

The solubility of a salt \( \text{MX} \) of a weak monobasic acid \( \text{HX} \) depends on pH according to the relation \( S = \sqrt{K_{sp}(1 + \frac{[\text{H}^+]}{K_a})} \). If \( K_{sp} = 4.0 \times 10^{-10} \) and \( K_a = 1.0 \times 10^{-5} \), what is the molar solubility of \( \text{MX} \) at \( \text{pH} = 3.0 \)?

1. A
   \( 2.0 \times 10^{-5}\text{ M} \)
2. B
   \( 6.32 \times 10^{-4}\text{ M} \)
3. C
   \( 2.01 \times 10^{-4}\text{ M} \)
4. D
   \( 4.00 \times 10^{-3}\text{ M} \)