Question

An aqueous buffer is prepared by adding 100 ml of 0.1 mol $l^{-l}$ acetic acid and 50 ml of 0.2 mol $l^{-1}$ of sodium acetate. If pKa of acetic acid is 4.76, the pH of the buffer is:

• A. 4.26
• B. 5.76
• C. 3.76
• D. 4.76

Answer 1

Answer: (D)

4.76

$pH=pKa+log\frac{\left[C{H}_{3}COONa\right]}{\left[C{H}_{3}COOH\right]}$

$pH=4.76+log\frac{50mL\times 0.2M}{100mL\times 0.1M}$

$pH=4.76+log1$

$pH=4.76$

The pH of the buffer is 4.76.