Question

In qualitative analysis, in order to detect second group basic radical, $H_{2}S$ gas is passed in the presence of dilute $HCl$ to:

• A. increase the dissociation of $H_{2}S$
• B. decrease the dissociation of salt solution
• C. decrease the dissociation of $H_{2}S$
• D. increase the dissociation of salt solution

Answer 1

The correct option is C decrease the dissociation of $H_{2}S$

In qualitative analysis, in order to detect second group basic radical, $H_{2}S$ gas is passed in the presence of dilute $HCl$ to Decrease the dissociation of $H_{2}S$.
Note: $HCl$ decreases ionization of $H_{2}S$ due to common ion effect so that only the solubility product of sulfides of group II radicals is overpowered and not that of III, IV and V group. Hence, group III, IV and V radicals are not precipitated by $H_{2}S$ in presence of $HCl$.