sebanyak 100 mL larutan CH3COOH 0,2 M dicampurkan dengan 100 mL larutan NaOH 0,2 M. jika Ka CH3COOH = 1 x 10⁻⁵ , maka pH larutan setelah dicampur adalah... a. 2

Diketahui: [CH3COOH]= 0,2 M
V = 100 mL
[NaOH] = 0,2 M
V = 100 mL
KaCH3COOH= 1×10^-5
Ditanya: pH.....?
Jawab
n CH3COOH=V×M
= 100×0,2= 20 mmol
n NaOH =V×M
= 100×0,2= 20 mmol
buat reaksi.
CH3COOH+NaOH->CH3COONa+H2O
A: 20mmol 20mmol - -
B: 20mmol 20mmol 20mmol 20mmol
___________________________________ _
S: - - 20mmol 20mmol

[H^+]= √Kw/Ka × (G)
G= 2/100= 0,2-> 2×10^-1
[H^+] = √10^-14/10^-5 × 2×10^-1
= √10^-9×2×10^-1
=√2×10^-8
=1×10^-4
pH = -log [OH^-]
= 4-log 1
= 4
jadi pH campurannya 4.