Question

Hitunglah pH larutan dari campuran 0,4 gram NaOH dengan 200mL larutan CH3COOH 0,4M (Ka=10^-5)

Answer 1

NaOH + CH3COOH --> CH3COONa + H2O
mol NaOH= gr/Mr = 0,4/40 = 0,01 mol
mol CH3COOH= MxV = 0,4 x 0,2 = 0,08 mol
mula2 : 0,01. 0,08. 0. 0
bereaksi: 0,01. 0,01. 0,01. 0,01
sisa: - 0,07. 0,01. 0,01
maka,
[H+] = ka. mol asam/mol garam
= 10^-5 x (0,07/0,01)
= 10^-5 x 7 = 7x10^-5 M
pH= -log [H+]
= -log 7x10^-5
= 5-log 7
= 4,15.