Question

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

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

Answer 1

The correct option is B 0.01 %

Given : $K_a=1\times {10}^{-5}M,\left[NaX\right]=0.1M$
Degree of hydrolysis for salt of weak acid and strong base is given by $h=\sqrt{\frac{K_w}{K_a\times c}}$
$h=\sqrt{\frac{{10}^{-14}}{{10}^{-5}\times 0.1}}\because K_w={10}^{-14}$
$h={10}^{-4}$
Hence, % degree of hydrolysis $h={10}^{-4}\times 100=0.01$