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

The pH of the solution is 4.28

Step-by-step explanation:

The dissolution reaction as below

CH₃COOH ⇔ CH₃COO⁻ + H⁺

`K_(a) = ([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