Question

$H_{2}S$ gas when passed through a solution of cations containing $HCl$ precipitates the cations of the second group of qualitative analysis but not those belonging to the fourth group. It is because:

• A. Presence of $HCl$ decreases the sulphide ion concentration.
• B. Sulphides of group IV cations are unstable in $HCl$
• C. The solubility product of group II sulphides is more than that of group IV sulphides
• D. Presence of $HCl$ increases the sulphides ion concentration

Answer 1

The correct option is A Presence of $HCl$ decreases the sulphide ion concentration.

Second group cations are precipitated as sulphides because of their law solubility products whereas sulphides of other metals remain in solution because of their high solubility products .$HCl$ acts as as source of $H^{+}$ which decrease the concentration of $S^{2-}$ ion is low that it exceeds only the solubility products of the metal sulphide of $I{I}^{nd}$ group .