An acidified solution of 0 . 05M Zn ^ 2 + is saturated with 0 . 1M...

For $ZnS$

${K}_{sp} ( ZnS ) = \left[{Zn}^{2 +}\right] \times \left[{S}^{2 -}\right] = 1 . 25 \times {10}^{- 22}$

$= 0 . 05 \times \left[{S}^{2 -}\right] = 1 . 25 \times {10}^{- 22}$

\left[{S}^{2 -}\right] = 25 \times {10}^{- 22}$</p><p>For${H}_{2}S$</p><p>$\mathop{{\text{H}_{2}\text{S}_{0 .1 M} ⇌ 2{\text{H}}^{+} + \mathop{{\text{S}}^{2 -}}_{25 \times {10}^{- 22}}$</p><p>${K}_{a} = \dfrac{\left[{H}^{'}\right]\left[{S}^{2 -}\right]}{\left[{H}_{2}S\right]} = 1 \times {10}^{- 21}$</p><p>$= \dfrac{{\left[{H}^{+}\right]}^{2} \times 25 \times {10}^{- 22}}{0 . 1} = 1 \times {10}^{- 21}$</p><p>${\left[{H}^{+}\right]}^{2} = \dfrac{1}{25}$</p><p>\left[{H}^{+}\right] = \dfrac{1}{5}$

\left[{H}^{+}\right] = 0 . 2M$