What molar ratio of acetic acid to sodium acetate is required to create a buffer solution having a pH of 4.83 at 25 Celsius? Ka for HC2H3O2 is 1.8 x10^-5 a)0.82 b)0.55 c)3.5 d)1.2 e)2.0

The answer I got was 8.2 ..(help!)

1 answer

Use the Henderson-Hasselbalch equation.
pH = pKa + log base/acic
4.83 = 4.74 + log(Ac^-)/(HAc)
(Ac^-)/(HAc) = 1.23 but the problem asks for the (acid)/(base) ratio to that is 1/1.23 = 0.82