100 ml larutan CH3COOH 0, 5 dicampur dengan 200 ml KOH 0, 1 M

CH3COOH +    KOH       => KCH3COO +        H2O
  50 mmol      20 mmol                  -                      -
  20 mmol      20 mmol            20 mmol          20 mmol
---------------------------------------------------------------------------
  30 mmol             -                  20 mmol          20 mmol

[H+]=Ka (a/g)
[H+]=10^-5 (30/20)
[H+]=10^-5*3*2^-1
pH=-log[H+]=-log10^-5*3*2^-1
pH = 5-log 3 + log 2

100 mL CH3COOH 0,5 M + 200 mL KOH 0,1 M
Ka = 10^-5

pH ... ?

n CH3COOH = M × V
n CH3COOH = 0,5 × 100
n CH3COOH = 50 mmol

n KOH = M × V
n KOH = 0,1 × 200
n KOH = 20 mmol

#Reaksi
... CH3COOH + KOH => CH3COOK + H2O
M : ..... 50 .......... 20
R : ...... 20 ......... 20
________________---
S : ...... 30 ......... --- ............. 20 ............ 20

[H^+] = Ka × Asam lemah/B. Konjugasi
[H^+] = 10^-5 × 30/20
[H^+] = 10^-5 × 1,5

pH = - log [H^+]
pH = - log 10^-5 × 1,5
pH = 5 - log 1,5