Question

Calculate the degree of hydrolysis $\left(h\right)$ of a salt of aniline and acetic acid in 0.1 M solution at ${25}^{\circ }C$
Given :
$K_a$ for $C{H}_{3}COOH$ is $1.8\times {10}^{-5}$
$K_b$ for aniline is $4.6\times {10}^{-10}$

• A. 0.996
• B. 0.235
• C. 0.85
• D. 0.523

Answer 1

The correct option is D 0.523

Since aniline and acetic acid are both weak electrolytes.
So,
$K_h=\frac{K_w}{K_a\times K_b}{K}_h=\frac{{10}^{-14}}{1.8\times {10}^{-5}\times 4.6\times {10}^{-10}}=1.2$

if we see, $\frac{K_h}{C}=\frac{1.2}{0.1}=12$
Since, $\frac{K_h}{C}<100$,
So we cannot take the approximation $1-h\approx 1$ and we have to solve quadratic,
$K_h=\frac{h^2}{(1-h{)}^2}\sqrt{K_h}=\frac{h}{1-h}\sqrt{1.2}=\frac{h}{1-h}1.096=\frac{h}{1-h}h=\frac{1.096}{2.096}=0.523$