What fraction of a 0.5 m acetic acid solution will be in the protonated form at ph 5.1? The pka of acetic acid is 4.8?

The acetic acid will dissociate as

We will use Hendersen Hassalbalch's equation here

pH = pKa + log [salt] / [acid]

Where

[Acid] = concentration of protonated form

5.1 = 4.8 + log [salt] / [acid]

1.99 = [salt] / [acid]

[salt] + [acid] = 0.5

1.99 [acid] + [acid] = 0.5

[acid] = 0.167 M

[acid] / total concentration = 0.167 / 0.5 = 0.33.4

So percentage = 33.4 % or approx 33 %