Question

The solubility product of $A{s}_2{S}_{3}is2.8\times {10}^{-72}$ What is the solubility of $A{s}_2{S}_3$

• A. $1.09\times {10}^{-15}$ mole / liter
• B. $1.72\times {10}^{-15}$ mole / liter
• C. $2.3\times {10}^{-16}$ mole / liter
• D. $1.65\times {10}^{-36}$ mole / liter

Answer 1

The correct option is A $1.09\times {10}^{-15}$ mole / liter

Let the solubility be S.

$A{s}_2{S}_3\leftrightharpoons 2A{s}^{3+}+3S^{2-}$

$2S$ $3S$

Solubility product is

$K_{sp}=\left[A{s}^{3+}{]}^2\right[S^{2-}{]}^3$

$K_{sp}=\left[2S{]}^2\right[3S{]}^3$

$K_{sp}=108\times S^5$

$S=\sqrt[5]{5\frac{K_{sp}}{108}}$

$=\sqrt[5]{5\frac{2.8\times {10}^{-72}}{108}}=1.09\times {10}^{-15}$mol/l