Question

How do the buffering capacity and ranges of the formate buffer (0.10M formic acid/formate buffer) compare to acetate buffer (0.10M 1:1 HAc and NaAc). Ka of formic acid: 1.8x10^-4 and Ka of acetic acid: 1.8x10^-5

Answer 1

Solution :-

Using the given ka values we can find the pka values of the acids

Pka= - log ka

Pka of acetic acid = - log [1.8*10^-4] = 4.74

Pka of formic acid = - log[1.8*10^-4] = 3.74

Buffering capacity is the pH range where the buffer works effectively and restrict the sudden pH change when the strong acid or base added to the buffer solution.

Since the Pka of the formic acid is 3.74 therefore its pH range is at about pH 3- 4 where it can effectively works as buffer.

Since the Pka of the acetic acid is 4.74 therefore its pH range is about pH 4 - 5 where acetic acid acetate buffer can effectively acts as buffer.