Question

Ionisation constant of each HA (Weak acid) and BOH (weak base) are $3.0\times {10}^{-7}$ each at $298\text{K}$. The percentage degree of hydrolysis of BA at the dilution of $10\text{L}$ is:

• A. 25
• B. 50
• C. 75
• D. 40

Answer 1

The correct option is A 25

Hydrolysis constant for a weak acid and weak base solution is given by
$K_h=\frac{K_w}{K_a{K}_b}$
lets say degree of hydrolysis is h then,
$\frac{h}{1-h}={\sqrt{K}}_h=(\frac{K_w}{K_a{K}_b}{)}^{1/2}$
$\frac{h}{1-h}=(\frac{{10}^{-14}}{3\times {10}^{-7}\times 3\times {10}^{-7}}{)}^{1/2}=\frac{1}{3}$
$\therefore h=0.25$