Question

If the dissociation constant of an acid $HA$ is $1\times {10}^{-5}$, the $pH$ of $0.1$ molar solution of the acid will be approximately :

• A. three
• B. five
• C. one
• D. six

Answer 1

The correct option is A three

$\left[H^{+}\right]=\sqrt{C{K}_a}$

$\left[H^{+}\right]=\sqrt{0.1\times {10}^{-5}}$

$\left[H^{+}\right]={10}^{-3}M$

$pH=-lo{g}_{10}\left[H^{+}\right]$

$pH=-lo{g}_{10}{10}^{-3}$

$pH=3$