Question

Calculate pH of a buffer prepared by adding 10 mL of 0.10 M acetic acid to 20 mL of 1 M sodium acetate [\( \text{CH}_3\text{COOH} \)] at \( \text{pH} = 4.74 \).

• A. 3.00
• B. 4.44
• C. 4.74
• D. 5.04

Hint:

Use the Henderson-Hasselbalch equation to calculate the pH of buffer solutions based on the concentrations of acid and conjugate base.

Answer 1

The Correct Option is D

Step 1: Henderson-Hasselbalch equation.
The pH of a buffer solution is calculated using the Henderson-Hasselbalch equation: \[ \text{pH} = \text{pKa} + \log \left( \frac{[\text{Salt}]}{[\text{Acid}]} \right) \] Substituting the given concentrations and pH value, we find the result.

Step 2: Conclusion.
The pH of the buffer is 5.04, corresponding to option (4).