Question

$K_{sp}$ of $Cu(OH{)}_2$ is 5 $\times {10}^{-16}$ at ${25}^{\circ }C$, then pH of a saturated solution of $Cu(OH{)}_2$ is___

Answer 1

for $Cu(OH{)}_2$, $K_{sp}=s\times (2s{)}^2=4s^3$ Here, the concentration of hydroxide ions is 2s
$s=\sqrt[3]{3\frac{Ksp}{4}}=$ $\sqrt[3]{3\frac{5\times {10}^{-16}}{4}}$
$=\sqrt[3]{3125\times {10}^{-18}}=5\times {10}^{-6}$

$\left[O{H}^{-}\right]=2s=2\times (5\times {10}^{-6})={10}^{-5}$
$pOH=5$ $pH=14-pOH=9$