Question

Calculate the degree of hydrolysis ($h$) of a $0.1M$ sodium acetate solution at $298K$.
Given: $K_a=1.8\times {10}^{-5}$

• A. $8.42\times {10}^{-5}$
• B. $7.42\times {10}^{-6}$
• C. $7.42\times {10}^{-5}$
• D. $8.42\times {10}^{-6}$

Answer 1

The correct option is C $7.42\times {10}^{-5}$

Hydrolysis constant for a salt of weak acid and strong base is given as:
$K_h=\frac{K_w}{K_a}=\frac{1\times {10}^{-14}}{1.8\times {10}^{-5}}=5.5\times {10}^{-10}$

Degree of hydrolysis is given as:
$h=\sqrt{\frac{K_h}{C}}=\sqrt{\frac{5.5\times {10}^{-10}}{0.1}}=(55\times {10}^{-10}{)}^{1/2}=7.42\times {10}^{-5}$