The reagent(s) that can selectively precipitate $S^{2-}$ from a mixture of $\mathrm{S}^{2-}$ and $\m

Question

The reagent(s) that can selectively precipitate $S^{2-}$ from a mixture of $\mathrm{S}^{2-}$ and $\mathrm{SO}_{4}^{2-}$ in aqueous solution is (are)\

Professor PC Thomas Classes · Answer

(a) : $\mathrm{Cu}^{2+}$ will give black precipitate of CuS while $\mathrm{CuSO}_{4}$ is soluble. $$ \begin{aligned} & \mathrm{Cu}^{2+}+\mathrm{S}^{2-} \longrightarrow \underset{	ext { Black precipitat }}{\mathrm{CuS} \downarrow} \ & \mathrm{Cu}^{2+}+\mathrm{SO}_{4}^{2-} \longrightarrow \underset{	ext { Soluble }}{\mathrm{CuSO}} \end{aligned} $$