Question

$HX$ is a weak acid $(K_a={10}^{-5})$. It forms a salt $NaX\left(0.1M\right)$ on reacting with caustic soda. The degree of hydrolysis of $NaX$ is:

• A. 0.01%
• B. 0.0001%
• C. 0.1%
• D. 0.5%

Answer 1

The correct option is A 0.01%

$X^{-}+H_{2}O\to HX+O{H}^{-}$

$K_h=\frac{K_w}{K_a}=\frac{{10}^{-14}}{{10}^{-5}}={10}^{-9}$

$K_h=C{\alpha }^2=0.1\times {\alpha }^2={10}^{-9}$

${\alpha }^2={10}^{-8}\Rightarrow \alpha ={10}^{-4}$

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