Question

The solubility of $Fe ( OH )_{3}$ is $x\, mol\, L ^{-1}$. Its $K_{s p}$ would be

• A. $9x^{3}$
• B. $3x^{3}$
• C. $27x^{4}$
• D. $9x^{4}$

Answer 1

Answer: (C)

$27x^{4}$

Answer 2

Dissociation of $Fe ( OH )_{3}$ in solution is represented as follows
$\underset{(-x)}{ Fe ( OH )_{3}} \rightleftharpoons \underset{(x)}{ Fe^{3+}} + \underset{(3x)}{3OH^-} K_{sp} = x \times (3x)^3 =27 x^{4}$