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