Sebanyak 25 ml larutan CH3COOH 0,2 M dicampurkan larutan NaOH 0,1 M maka harga pH larutan yang terjadi adalah

CH3COOH + NaOH → CH3COONa + H2O

→ CH3COOH
m = 0,2 x 25 = 5 mmol
r = 2,5 mmol
s = 2,5 mmol

→ NaOH
m = 0,1 x 25 = 2,5 mmol
r = 2,5 mmol
s = -

→ CH3COONa
m = -
r = 2,5 mmol
s = 2,5 mmol

→ H2O
m = -
r = 2,5 mmol
s = 2,5 mmol

[H+] = Ka . (sisa asam / sisa garam)
[H+] = 10^-5 . (2,5 / 2,5)
[H+] = 10^-5

pH = -log [H+]
pH = -log10^-5
pH = 5