Question

A weak acid $HX$ has the dissociation constant $1\times {10}^{-5}M$, It forms a salt $NaX$ in reaction with alkali. The degree of hydrolysis of $0.1M$ solution if $NaX$ is:

• A. $0.0001$%
• B. $0.01$%
• C. $0.1$%
• D. $0.15$%

Answer 1

Answer: (B)

$0.01$%

$X^{-}+H_{2}O\rightleftharpoons HX+{OH}^{-}$

$K_h=\frac{{10}^{-14}}{{10}^{-5}}$

So, degree of hydrolysis
$x=\sqrt{\frac{K_h}{C}}=\sqrt{\frac{{10}^{-9}}{{10}^{-1}}}={10}^{-4}$

% degree of hydrolysis $={10}^{-4}\times 100=0.01$