Question

The solubility product of sparingly soluble salt $A{g}_{2}Cr{O}_4$ is $4\times {10}^{-12}$. The molar solubility of the salt is ${10}^{-x}mol/L$? What is the value of $x$?

Answer 1

$AgCr{O}_4$ dissociates in solution as

$AgCr{O}_4\left(aq\right)⟷2A{g}^{+}+Cr{O}_4^{-}$

$\left[A{g}^{+}\right]=2S$

$\left[Cr{O}_4^{-}\right]=S$

$Ksp=\left[A{g}^{+}{]}^2\right[Cr{O}_4^{-}]$

$=\left(2S{)}^2\right(S)$

$=4S^3$

$4S^3=40\times {10}^{-12}$

$S={10}^{-4}$

$⟶x=4$