H2S gas when passed through a solution of cations containing HCl precipitates the cations of second group of qualitative analysis but not those belonging to the fourth group. It is because:
1. | Presence of HCl decreases the sulphide ion concentration |
2. | Sulphides of group IV cations are unstable in HCl |
3. | Solubility product of group II sulphides is more than that of group IV sulphides |
4. | Presence of HCl increases the sulphides ion concentration |