Question

The solubility product of $A _{2} X _{3}$ is $1.08 \times 10^{-23}$. Its solubility will be

• A. $1.0 \times 10^{-3} M$
• B. $1.0 \times 10^{-4} M$
• C. $1.0 \times 10^{-5} M$
• D. $1.0 \times 10^{-6} M$

Answer 1

Answer: (C)

$A _{2} X _{3} \rightleftharpoons 2 A ^{+3}+3 X ^{-2}$
$Ksp =\left[ A ^{+3}\right]^{2}\left[ X ^{-2}\right]^{3}$
$=(2 S )^{2}(3 S )^{3}=108 S ^{5}$
$S =\frac{ Ksp ^{1 / 5}}{108}=\frac{1.08 \times 10^{-231 / 5}}{108}$
$S =\left[10^{-25}\right]^{1 / 5}=10^{-5}$