Question

The solubility product of a salt having general formula $M{X}_2$ in water is :

$4\times {10}^{-12}$. The concentration of $M^{2+}$ ions in the aqueous solution of the salt

is

• A. $2.0\times {10}^{-6}M$
• B. $1.0\times {10}^{-4}M$
• C. $1.6\times {10}^{-4}M$
• D. $4\times {10}^{-10}M$

Answer 1

The correct option is B

$1.0\times {10}^{-4}M$

$M{X}_2\leftrightharpoons M^{+}+2X^{-}$;
At equilibrium, $\left[M^{+}\right]=s,\left[X^{-}\right]=2s$
$K_{sp}=4s^3$

$s$ = $\sqrt[3]{3\frac{K_{sp}}{4}}=\sqrt[3]{3\frac{1\times {10}^{-12}}{4}}=1.0\times {10}^{-4}M$