Question

What is the pH of a solution that is 0.10 M formic acid and 0.0065 M formate (the conjugate base)? Ka of formic acid = 1.77 x 10-4

Answer 1

Answer:

pH = 2.56

Explanation:

The Henderson-Hasselbalch equation relates the pH to the Ka and ratio of the conjugate acid-base pair as follows:

pH = pKa + log([A⁻]/[HA]) = -log(Ka) + log([A⁻]/[HA])

Substituting in the value gives:

pH = -log(1.77 x 10⁻⁴) + log((0.0065M) / (0.10M))

pH = 2.56