Answer
pH of buffer = 3.89
Work Step by Step
1
(A) Given :
1. [conjugate base] = [HCOO-] = 0.63 M
2. [acid] = [HCOOH] = 0.45 M
3. pKa of acid (HCOOH) = 3.74
2
(B) Formulae :
1. Henderson - Hasselbalch equation of a buffer :
pH = pKa + log [conjugate base] / [acid]
3
(C) Solution :
pH = pKa + log [conjugate base] / [acid]
So,
pH = 3.74 + log (0.63 / 0.45)
3.74 + 0.15
= 3.89
Hence, pH of the buffer is 3.89.
4
(D) Answer :
pH of buffer = 3.89
