Question

The $pH$ of a certain centimolar solution of a monobasic acid $HA$ is $6.0$. The dissociation constant of the acid is approximately equal to:

• A. ${10}^{-12}$
• B. ${10}^{-8}$
• C. ${10}^{-10}$
• D. ${10}^{-6}$

Answer 1

The correct option is C ${10}^{-10}$

The concentration of centimolar solution is $0.01$ M and its $pH$ is $6.0$.

Its hydrogen ion concentration will be ${10}^{-6}M$.

The relationship between the hydrogen ion concentration and dissociation constant is $\left[H^{+}\right]=\sqrt{K_a\times c}$

Substitute values in the above expression,
${10}^{-6}=\sqrt{K_a\times 0.01}$

Hence, $K_a={10}^{-10}$.

Option C is correct.