Question

The solubility product of $As _{2} O _{3}$ is $10.8 \times 10^{-9}$. It is $50 \%$ dissociated in saturated solution. The solubility of salt is

• A. $10^{-2}$
• B. $ 2\times 10^{-2}$
• C. $ 5\times 10^{-3}$
• D. $ 5.4\times 10^{-9}$

Answer 1

Answer: (B)

$As _{2} O _{3} \rightleftharpoons 2 As ^{3+}+3 O ^{2-}$
$K_{s p} =(2 S)^{2}(3 S)^{3}$
$10.8 \times 10^{-9} =108 S^{3}$
$S =10^{-2}$
If dissociation is $50 \%$ then solubility is $2 \times 10^{-2} mol / L$.