Indentify the correct order of solubility in aqueous medium

Options

A. `ZnSgtNa_(2)SgtCuS`
B. `Na_(2)SgtCuSgtZnS`
C. `Na_(2)SgtZnSgtCuS`
D. `CuSgtZnSgtNa_(2)S`

Answer

C

Explanation

All alkali metal (group 1A or 1) compounds are soluble. In salt analysis, the sulphides of group 2 `(CuS, CdS, SnS, Bi_(2)S_(3))` have low solubility product relative to the sulphides of group 3 `(CoS, FeS, MnS, Nis, ZnS)`. If two compounds (such as CuS and ZnS) have the same ion ratio, the one with larger `K_(sp)` will have the higher molar solubility. Thus, ZnS is more soluble than CuS.