Question

The solubility product of a salt having formula $M_2{X}_3$ is $2.2\times 10^{-20}$. If the solubility of an another salt having formula $M_{2}X$ is twice the molar solubility of $M_2{X}_3$, the solubility product of $M_{2}X$ is

• A. $3\times 10^{-12}$
• B. $9.16\times 10^{-5}$
• C. $4.58\times 10^{-5}$
• D. $2.76\times 10^{-18}$

Answer 1

Answer: (A)

or $2.2\times 10^{-20}=108s^5$
$\therefore s=4.59\times 10^{-5}$
For $M_{2}X$
$M_{2}X\rightleftharpoons \underset{2s}{2}{M}^{+}+{\underset{s}{X}}^{2-}$
$K_{sp}=(2s{)}^2\cdot (s)$
$K_{sp}=4s^3$
$K_{sp}=4{\left(2\times 4.59\times 10^{-5}\right)}^3$
$[\because$ Solubility of $M_{2}X=2\times$ solubility of $M_2{X}_3]$
$=3\times 10^{-12}$