Question

The ka value for acetic acid, ch3cooh(aq), is 1.8× 10–5. calculate the ph of a 2.20 m acetic acid solution.

Answer 1

Answer is: pH value of acetic acid is 2.2.
Chemical reaction: CH₃COOH(aq) ⇄ CH₃COO⁻(aq) + H⁺(aq).
Ka(CH₃COOH) = 1,8·10⁻⁵.
c(CH₃COOH) = 2,2 M
[CH₃COO⁻] = [H⁺] = x.
Ka = [CH₃COO⁻] · [H⁺] / [CH₃COOH].
1,8·10⁻⁵ = x² / (2,2 M - x).
Solve quadratic equation: x = [H⁺] = 0,0063 M.
pH = -log[H⁺].
pH = -log(0,0063 M).
pH = 2,2.