Page 51 - E-Modul Kimia

E-MODUL KIMIA 2022

8. Diketahui :
M NH 3 = 0,01 M

V NH 3 = 10 ml

Mr (NH 4) 2SO 4 = 132
-5
K b = 2 × 10
pH = 9
Ditanya : massa (NH 4) 2SO 4 ?

Jawab :
a. Cari POH

POH = 14 – pH

= 14- 9
= 5
-
b. Cari [OH ]
-
POH = -log [OH ]
-
5 = - log [OH ]
-
-5
[OH ] = 10
c. Cari mol

Mol basa lemah = M × V
= 0,01 M × 10 mL

= 0,1 mol

;
[ ] = × ℎ

2×
;
[ ] = 2 × 10 ;5 × 0,1
2×
10 ;5 = 2 × 10 ;5 × 0,1
2×
10 −5 = 0,1
10 −5
0,1
1 =

= 0,1

Maka massa garam (NH 4) 2SO 4 =

=

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