Q38 / 180 · KCET 2011 · Chemistry
$\mathrm{H}_{2} \mathrm{~S}$ is passed into one $\mathrm{nm}^{3}$ of a solution containing $0.1$ mole of $\mathrm{Zn}^{2+}$ and $0.01$ mole of $\mathrm{Cu}^{2+}$ till the sulphide ion concentration reaches to $8.1 \times 10^{-19}$ moles. Which one of the following statements is true?
$\left[K_{\mathrm{sp}}\right.$ of $\mathrm{ZnS}$ and CuS are $3 \times 10^{-22}$ and $8 \times 10^{-36}$ respectively.]
- AOnly $\mathrm{ZnS}$ precipitates
- Correct answerBBoth CuS and $\mathrm{ZnS}$ precipitate
- COnly CuS precipitates
- DNo precipitation occurs
Solution
The ionic product for $\mathrm{ZnS}\left(0.1 \times 8.1 \times 10^{-19}\right)$ and for CuS $\left(0.01 \times 8.1 \times 10^{-19}\right)$ exceeds their $K_{\mathrm{sp}}$ values. Hence, both get precipitated.
Hence, the correct answer is option: 'B'.