Question

Calculate the $pH$ of buffer solution prepared by mixing $50$ ml of $0.1$ M sodium acetate and $25$ ml of $0.2$ M $C{H}_{3}COOH$ if $p{K}_a$ of $C{H}_{3}COOH$ is $4.8$.

• A. $4.8$
• B. $10.2$
• C. $5.8$
• D. $14$

Answer 1

The correct option is A $4.8$

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

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

$p{K}_a=4.8$

$\left[salt\right]=\frac{50\times 0.1}{1000}=0.005M$

$\left[acid\right]=\frac{25\times 0.2}{1000}=0.005M$

Substitute values in the above equation.

$pH=4.8+log\left(\frac{0.005}{0.005}\right)=4.8$.

Option A is correct.