Chemistry - Salt Analysis Question with Solution | TestHub

IV ${}^{\text{th }}$ group needs higher ${\mathrm{S}}^{2-}$ ion concentration. In presence of $\mathrm{HCl}$, the dissociation of ${\mathrm{H}}_2\mathrm{S}$ decreases hence produces less amount of sulphide ions due to common ion effect, thus $\mathrm{HCl}$ decreases the solubility of ${\mathrm{H}}_2\mathrm{S}$ which is sufficient to precipitate II ${}^{\text{nd }}$ group radicals.