Concentration of the ${\mathrm{Ag}}^{+}$ ions in a saturated solution of ${\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4$ is $2.2 \mathrm{x} {10}^{-4}$ mol  $L^{-1}$ . Solubility product of ${\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4$ is

$$\begin{gathered} \text{ Let solubility of }{\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4\text{ be }\mathrm{s} \mathrm{mol}{ \mathrm{L}}^{-1} \\ {\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_{4\left(\mathrm{s}\right)}\rightleftharpoons 2{\mathrm{Ag}}_{\left(\mathrm{aq}\right)}^{+}+{\mathrm{C}}_2{\mathrm{O}}_{4\left(\mathrm{aq}\right)}^{2-} \\ {\mathrm{K}}_{\mathrm{sp}}=\left(2\mathrm{s}{)}^2\right(\mathrm{s})\Rightarrow 4{\mathrm{s}}^3 \\ {\mathrm{K}}_{\mathrm{sp}}=4\times {\left(1.1\times {10}^{-4}\right)}^3 \left(\because \left[{\mathrm{Ag}}^{+}\right]=2\mathrm{s}=2.2\times {10}^{-4}\right) \\ {\mathrm{K}}_{\mathrm{sp}}\approx 5.3\times {10}^{-12} \end{gathered}$$