`H_(2)S` gas when passed through a solution of cations containing `HCl` precipitates the cations of second group in qualitative analysis but not those belonging to the fourth group. It is because

Options

A. Presence of HCl decreases the sulphide ion concentration
B. Presence of HCl increases the sulphide ion concentration
C. Solubility product of group II sulphides is more than that of group IV sulphides
D. Sulphides of group IV Cations are in HCl

Answer

A

Explanation

In qualitative analysis of cations of group II `H_(2)S` gas is passed in presence of HCl, of sulphide ions is obtained which is sufficient for the precipitation of second group cations in form of their sulphides due to lower value of their solubility product `(K_(sp))`.
Here, fourth group cations are not precipitated because they require for exceeding their ionic product to their solubility products and higher sulphide ion concentration due to their higher `K_(sp)` which is not obtained here due to common ion effect.