Question

pH of 0.1 M weak acid solution is 4. What is the dissociation constant of the acid ?

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

$P^H=-log\left[H^{+}\right];\left[H^{+}\right]={10}^{-P^H}={10}^{-4}M\left[H^{+}\right]=\sqrt{K_a\times C};K_a=\frac{[H^{+}{]}^2}{C}=\frac{\left({10}^{-4}\right)}{0.1}={10}^{-7}$