Question

Question 2.27

If the solubility product of CuS is $6\times {10}^{-6}$, calculate the maximum molarity of CuS in aqueous solution.

Answer 1

Chemical equation for the dissociation of CuS in aqueous solution is as follows:

Molar concentration $\underset{\left[S\right]}{CuS\left(s\right)}\stackrel{H_{2}O}{\rightleftharpoons }\underset{\left[S\right]}{C{u}^{2+}\left(aq\right)}+\underset{\left[S\right]}{S^{2-}\left(aq\right)}$

Solubility product, $K_{sp}=\left[C{u}^{2+}\right]\left[S^{2-}\right]$

$=S\times S=S^2$

$6\times {10}^{-16}=S^2$

$S=\sqrt{6\times {10}^{-16}}or(6\times {10}^{-16}{)}^{\frac{1}{2}}$

$=24.5\times {10}^{-8}mol{L}^{-1}$

$2.45\times {10}^{-8}M$