Identify the correct order of solubility of `Na_(2)S, CuS` and ZnS in aqueous solution :

Options

A. `CuS gt ZnS gt Na_(2)S`
B. `ZnS gt Na_(2)S gt CuS`
C. `Na_(2)S gt CuS gt ZnS`
D. `Na_(2)S gt ZnS gt CuS`

Answer

D

Explanation

Sodium sulphide `(Na_(2)S)` is a strong electrolyte and it readily ionises in aqueous solution. Out of ZnS and CuS, the latter gets precipitated more easily because its `ksp (8.5 xx 10^(-45))` is less than that of `ZnS (2.5 xx 10^(-22))`. Therefore the correct order of solubility is: `Na_(2)S gt ZnS gt CuS`