Question

Calculate the pH of buffer solution prepared by mixing $50\text{ml}\text{of}0.1\text{M}$ sodium acetate and $25\text{ml of}0.2\text{M}$ $C{H}_{3}COOH\text{if}{\text{pK}}_a\text{of}C{H}_{3}COOH$ 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.
${\text{pH = pK}}_a+\log \frac{\left[\text{salt}\right]}{\text{[acid]}}$
${\text{pK}}_a=4.8$
$\left[\text{salt}\right]=\frac{50\times 0.1}{75}=0.067\text{M}$
$\left[\text{acid}\right]=\frac{25\times 0.2}{75}=0.067\text{M}$
Substitute values in the above equation.
$\text{pH}=4.8+\log \left(\frac{0.067}{0.067}\right)=\mathrm{4.8.}$