Question

Solubility of $Mg(OH{)}_2$ having $K_{sp}$ equal to $8.9\times {10}^{-13}$ , in a solution containing 500 ml of 0.2 M $N{H}_{4}OH$ and 500 ml of 0.4 M $Ca(OH{)}_2$ is:

• A. $3.4\times {10}^{-19}$
• B. $55.63\times {10}^{-13}$
• C. $2.34\times {10}^{-9}$
• D. $8.34\times {10}^{-13}$

Answer 1

The correct option is B $55.63\times {10}^{-13}$

Let S be the solubility of $Mg(OH{)}_2$.

$S=\left[M{g}^{2+}\right]=\frac{K_{sp}}{[O{H}^{-}{]}^2}$

$S=\frac{8.9\times {10}^{-13}}{(0.4{)}^2}=55.63\times {10}^{-13}$.

Hence, the correct option is $\text{B}$