Question

The solubility of magnesium hydroxide in pure water is $8.2\times {10}^{-5}$mol per 500ml of water. The solubility product of magnesium hydroxide is

• A. $6.72\times {10}^{-9}{M}^2$
• B. $5.51\times {10}^{-13}{M}^3$
• C. $8.84\times {10}^{-12}{M}^3$
• D. $1.77\times {10}^{-11}{M}^3$

Answer 1

The correct option is D $1.77\times {10}^{-11}{M}^3$

The solubility of magnesium hydroxide in pure water is $8.2\times {10}^{-5}$ mol per 500ml of water.

It is equal to $2\times 8.2\times {10}^{-5}=1.64\times {10}^{-4}$ mol per 1000ml of water.

The expression for the solubility product of magnesium hydroxide is $K_{sp}=\left[M{g}^{2+}\right][O{H}^{-}{]}^2$.

Substitute values in the above expression.

$K_{sp}=(1.64\times {10}^{-9})(2\times 1.64\times {10}^{-9}{)}^2=1.77\times {10}^{-11}{M}^3$.