Question

What is the pH of a solution that contains three parts of acetic acid and one part sodium acetate? The p K for acetic acid is 4.76.

Answer 1

Answer:

The pH of the solution is 4.28

Explanation:

The dissolution reaction as below

CH₃COOH ⇔  CH₃COO⁻ + H⁺

$K_{a} = \frac{[CH_{3}COO^{-}][H^{+}]}{[CH_{3}COOH} = 10^{-4.76}$

Assume the concentration of the ion, [H⁺] = a,

          so [CH₃COO⁻] = a and [CH₃COOH] = 3a

Then use the formula of Ka, we get

Ka = a * a / 3a = 10^-4.76 ⇔ a = 3 x 10^-4.76 = 5.21 x 10^-5

Hence pH = -log(a) = - log(5.21 x 10^-5) = 4.28