Question

Tentukan pH campuran 200ml larutan KOH 2,24 M dengan 500ml larutan CH₃COOH 0,896 M jika Ka = 1,6 x 10⁻⁶

Answer 1

NKOH=448mmol
nCH₃COOH=448mmol
KOH+CH₃COOH----->CH₃COOK+H₂O
448      448                   -
448      448                448            448  _
-             -                  448
n CH3COOK=448
V=200ml+500ml=700ml
M=n/V=448/700=0,64
OH=√[(kw/ka)*M]
OH=√[(10⁻14/1,6*10⁻6)*0,64
OH=4*10⁻5
pOH=-log 4*10⁻5=5-log4
pH=14-pOH=9+log4

Answer 2

Mol KOH = 200 x 2,24 = 448 mmol
mol CH₃COOH = 500 x 0,896 = 448 mmol

Persamaan reaksi :
     CH₃OOK + KOH → CH₃COOK + H₂O
a    448            448
r     448            448
___________________________________
s      -                 -            448 mmol

mol CH₃COOK yang terbentuk = 448 mmol

M CH₃COOK = mol/Volume campuran
M CH₃COOK = 448/(200 + 500)
M CH₃COOK = 448/700
M CH₃COOK = 0,64 M

Pakai rumus Hidrolisis Garam
[OH⁻] = √Kw/Ka • M Garam
[OH⁻] = √10⁻¹⁴/1,6 x 10⁻⁶ • 0,64
[OH⁻] = √4 x 10⁻⁹
[OH⁻] = 2 x 10^⁻4,5

pOH = -log [OH⁻]
pOH = -log [2 x 10^-4,5]
pOH = 4,5 - log 2

pH = 14 - pOH
pH = 14 - (4,5 - log 2)
pH = 9,5 + log 2
pH = 9,8

Jadi, pH campuran adalah 9,8