Question

The solubility product $K_{sp}$ for $B{i}_2{S}_3$ is $1.2\times {10}^{-98}$. The solubility of $B{i}_2{S}_3$ is approximately:

• A. $1\times {10}^{-33}$
• B. $1\times {10}^{-20}$
• C. $1\times {10}^{-27}$
• D. $1\times {10}^{-24}$

Answer 1

The correct option is B $1\times {10}^{-20}$

$K_{sp}\left(B{i}_2{S}_3\right)=\left[B{i}^{3+}{]}^2\right[S^{2-}{]}^3=(2s{)}^2\times (3s{)}^3=1.2\times {10}^{-98}$

$K_{sp}=108s^5=1.2\times {10}^{-98}$

$s^5=\frac{1.2}{108}\times {10}^{-98}$

$s^5\simeq 1\times {10}^{-100}$

Hence, $s\simeq 1\times {10}^{-20}$.