Question

Hydrolysis constant of a salt $NaX$ is ${10}^{‑8}$ The pH of 0.01 M solution of the weak acid $HX$ is

• A. 8
• B. 4
• C. 12
• D. 6

Answer 1

The correct option is A

8

$K_h$ = $\frac{K_w}{K_a}$; $K_a$ = $\frac{K_w}{K_h}$ = $\frac{{10}^{-14}}{{10}^{-8}}$ = ${10}^{-6}$

$p^{K_a}$ = $-log\left(K_a\right)$ = $-log\left({10}^{-6}\right)$ = $6$

$P^H$ = $\frac{1}{2}{P}^{K_w}$ + $\frac{1}{2}{P}^{K_a}$ + $\frac{1}{2}log\left(C\right)$ = $\frac{1}{2}\times 14+\frac{1}{2}\times 6+\frac{1}{2}log\left({10}^{-2}\right)$ = $8$