Q78 / 270 · NDA 2018 (Phase 2) · General Ability

Permanent hardness of water cannot be removed by which one of the following methods?

A
Treatment with washing soda
B
Calgon's method
Correct answer
C
Boiling
D
Ion exchange method

Solution

The permanent hardness of water is due to presence of chloride and sulphates salts of calcium and magnesium. This type of hardness can be removed by Calgon's method, Ion-exchange method and treatment with washing soda. Boiling can remove only the temporary hardness of water but not the permanent hardness.

Hence, the correct answer is option: 'C'.

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