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e-modul KIMIA 2022

15. A. 4 – log 1,92
Pembahasan:
Reaksinya:
HCOOH + KOH  HCOOK
m = 10 mmol 0,2 mmol 10 mmol
r = -0,2 mmol -0,2 mmol +0,2 mmol
s = 9,8 mol – 10,2 mmol

[H ] = Ka x
+

9,8
= 2 x 10 x
-4
10,2
-4
= 1,92 x 10
pH = - log [H ]
+
= - log 1,92 x 10
-4
= 4 – log 1,92

16. C. 9,28
Pembahasan:
2-
+
(NH4)2SO4  2NH4 + SO4
250 mmol 500 mmol
Reaksinya:
H2SO4 + 2 NH4OH  (NH4)2SO4
m = 5 mmol 500mmol 500mmol
r = -5 mmol -10mmol +5 mmol
s = - 490 mmol 10+500 mmol

+
(NH4)2SO4  2NH + SO4 2-

[OH ] = Kb x
-

= Kb x

490
= 2 x 10 x
-4
510
= 1,92 x 10
-5
pOH = - log [OH ]
-
= - log 1,92 x 10
-5
= 5 – log 1,92
pH = 14 –(5 – log 1,92)
= 9 + log 1,92
= 9,28

e-modul Kesetimbangan Ion dan pH Larutan Penyangga Halaman 64