The ka values for several weak acids are given below. which acid (and its conjugate base) would be the best buffer at ph = 8.0?

One of the best buffer choice for pH = 8.0 is Tris with Ka value of 6.3 x 10^-9.

To support this answer, we first calculate for the pKa value as the negative logarithm of the Ka value:

pKa = - log Ka

For Tris, which is an abbreviation for 2-Amino-2-hydroxymethyl-propane-1,3 - diol and has a Ka value of 6.3 x 10^-9, the pKa is

pKa = - log Ka

= - log (6.3x10^-9)

= 8.2

We know that buffers work best when pH is equal to pKa:

pKa = 8.2 = pH

Therefore Tris would be a best buffer at pH = 8.0.