hitunglah ph campuran antara 400 ml hno2 0.4m dengan 100ml NaOH 0.5m diketahui HNO2 mempunyai ka :5.1 x 10^-4

mol HNO2 = 400 x 0.4 = 160 mmol
mol NaOH = 100 x 0.5 = 50 mmol

......HNO2 + NaOH => NaNO2 + H2O
m 160..........50
r..........-50.......-50............+50............+50
s........110............-.................50..............50

larutan buffer,
[H+] = ka x ca/cg
[H+] = 5.1 x 10^-4 x 110/50 = 11.22 x 10^-4
pH = 4 - log 11.22