JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Equilibrium

The dissolution of sparingly soluble $\mathrm{AgCl}$ is governed by $K_{sp}=[\mathrm{A}{\mathrm{g}}^{+}][\mathrm{C}{\mathrm{l}}^{-}]$. Any solution that already supplies $\mathrm{A}{\mathrm{g}}^{+}$ or $\mathrm{C}{\mathrm{l}}^{-}$ pushes this equilibrium backward through the common-ion effect: $\mathrm{KCl}$ and $\mathrm{HCl}$ each contribute $\mathrm{C}{\mathrm{l}}^{-}$, while $\mathrm{AgN}{\mathrm{O}}_3$ contributes $\mathrm{A}{\mathrm{g}}^{+}$, so in all three the solubility is suppressed. Deionised water contains no common ion, so nothing shifts the equilibrium and $\mathrm{AgCl}$ dissolves to its greatest extent there.