Q. A buffer solution contains 0.1 mole of sodium acetate dissolved in $1000\ cm^{3}$ of 0.1 M acetic acid. To the above buffer solution, 0.1 mole of sodium acetate is further added and dissolved. The pH of the resulting buffer is
A) ${pK}_{a}$
B) ${pK}_{a} + 2$
C) ${pK}_{a} - \log 2$
D) ${pK}_{a} + \log 2$
Explanation
(d)
Initially $\left\lbrack CH_{3}COONa \right\rbrack = 0.1\ mol$
$\left\lbrack CH_{3}COOH \right\rbrack = 0.1\ mol$
when 0.1 mol $CH_{3}COONa$ is added.
$\left\lbrack CH_{3}COONa \right\rbrack = 0.1 + 0.1 = 0.2\ mol$
pH = $pK_{a} + \log\frac{\lbrack salt\rbrack}{\lbrack acid\rbrack}$
$= pK_{a} + \log\frac{0.2}{0.1}$
$= pK_{a} + \log 2$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.