Jika 100 mL larutan Hcl 0,1 M dicampurkan dengan 100 mL larutan NH3 0,3M (Kb=10^-5),pH larutan adalah

HCl + NH3 → NH4Cl

→ HCl :
m = 100 x 0,1 = 10 mmol
r = 10
s = -

→ n NH3 :
m = 100 x 0,3 = 30 mmol
r = 10
s = 20 mmol

→ NH4Cl :
m = -
r = 10
s = 10 mmol

[OH-] = Kb . 20 / 10
[OH-] = 10^-5 . 2
[OH-] = 2 x 10^-5

pOH = -log[OH-]
pOH = -log 2 x 10^-5
pOH = 5 - log2

pH = 14 - (5 - log2)
pH = 14 - 5 + log2
pH = 9 + log2