Question

Find the change in pH when 0.01 mole $C{H}_{3}COONa$ is added to one litre of 0.01 M $C{H}_{3}COOH$. $p{K}_a=4.74$

• A. 3.27
• B. 4.74
• C. 1.37
• D. 2.74

Answer 1

The correct option is C 1.37

$pH=\frac{1}{2}p{K}_A-\frac{1}{2}logC$

$\Rightarrow \frac{1}{2}\times 4.74-\frac{1}{2}log\left[{10}^{-2}\right]=2.37+1=3.37$

pH of buffer = $p{K}_A+log\frac{\left(Salt\right)}{\left(Acid\right)}$

pH of buffer = $4.74+log\frac{\left(0.01\right)}{\left(0.01\right)}$ = 4.74

Change in pH = 4.74 − 3.37 = 1.37

Hence, correct option is C.