Question

Solubility of a $M_{2}S$ type salt is $3.5\times 10^{-6}$ ,then find out its solubility product

• A. $1.7\times 10^{-6}$
• B. $1.7\times 10^{-16}$
• C. $1.7\times 10^{-18}$
• D. $1.7\times 10^{-12}$

Answer 1

Answer: (B)

Solubility of $M_{2}S$ salt is $3.5\times 10^{-6}M$
$\underset{3.5\times 10^{-6}M}{M_{2}S}\rightleftharpoons \underset{2\times 3.5\times 10^{-6}M}{2M^{+}}+\underset{3.5\times 10^{-6}M}{S^{2-}}$
$\therefore$ ( on $100\%$ ionisation)
$\therefore K_{sp}$ (Solubility product of $M_{2}S$ )
$={\left[M^{+}\right]}^2\left[S^{2-}\right]$
$={\left(7.0\times 10^{-6}\right)}^2\left(3.5\times 10^{-6}\right)$
$=171.5\times 10^{-18}=1.71\times 10^{-16}$