Question

A buffer solution is prepared by mixing 10 ml of 1.0 M acetic acid & 20 ml of 0.5 M sodium acetate and then diluted to 100 ml with distilled water. If the $p{K}_a$ of $C{H}_{3}COOH$ is 4.76. What is the pH of the buffer solution prepared?

• A. 3.84
• B. 4.76
• C. 4.34
• D. 5.21

Answer 1

Answer: (B)

4.76

The expression for the pH of the acidic buffer solution is as given below.

$pH=p{K}_a+log\frac{\left[Salt\right]}{\left[Acid\right]}$

$p{K}_a=4.76$

$\left[Salt\right]=\frac{20\times 0.5}{100}=0.1M$

$\left[Acid\right]=\frac{10\times 1}{100}=0.1M$

Substitute values in the above equation.

$pH=4.76+log\frac{0.1}{0.1}=4.76$.

So, the correct option is $B$