Name

Question

acetic

Ka

1.8 x 10-5

4.5 x 10-7

H3C6H507 3.2 x 10-7

pKa

4.7

Suppose that you were asked to create a buffer solution that buffers around a
pH of 6. As a general rule, if you were asked to select an acid for the
preparation of a buffer solution, you would choose an acid that has a pKa
close to your desired pH (this will give your buffer nearly equivalent amounts
of acid and conjugate base so it will be able to neutralize as much H+ and OH-
as possible). Using the chart below, which acid would you choose to create
your buffer?

Formula

HC2H3O2

carbonic (I) H2CO3

citric (I)

sulfurous
(II)

6.3

6.5

HSO3

6.3 x 10-8

7.2

Answer 1

Based on the pKa values provided, the acid that would be the best choice to create a buffer solution with a pH of 6 is carbonic (I) H2CO3, as its pKa value is closest to the desired pH of 6.5.