How much volume of `0.1M Hac` should be added to `50mL` of `0.2M NaAc` solution to have a `pH 4.91`?

Explanation

To solve the problem of how much volume of 0.1 M acetic acid (HAc) should be added to 50 mL of 0.2 M sodium acetate (NaAc) to achieve a pH of 4.91, we can use the Henderson-Hasselbalch equation, which is given by:

\[ \text{pH} = \text{pKa} + \log\left(\frac{[\text{Salt}]}{[\text{Acid}]}\right) \]

### Step 1: Identify the pKa of acetic acid
The pKa of acetic acid is approximately 4.76.
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