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Question
Chemistry
Which one of the following is not a method to remove permanent hardness of water?
Q. Which one of the following is not a method to remove permanent hardness of water?
1457
229
TS EAMCET 2015
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A
Clark's method
B
Calgon method
C
lon-exchange method
D
Synthetic resins method
Solution:
Clark's method is not used to remove permanent hardness of water. This method is used to remove temporary hardness of water.
C
a
(
H
C
O
3
)
2
+
C
a
(
O
H
2
)
⟶
2
C
a
C
O
3
↓
+
2
H
2
O
M
g
(
H
C
O
3
)
2
+
2
C
a
(
O
H
)
2
⟶
2
C
a
C
O
3
↓
+
M
g
(
O
H
)
2
↓
+
2
H
2
O
If excess of lime is added, water will again become hard because of adsorption of
C
O
2
from the atmosphere.
C
a
(
O
H
2
)
+
2
C
O
2
⟶
C
a
(
H
C
O
3
)
2