Question

Which of the following methods are used to remove temporary hardness of water? I) Boiling
II) Calgon method
III) Clark's method

• A. I only
• B. I& III only
• C. II only
• D. I, II& III

Hint:

Remember: Boiling and Clark’s method target temporary hardness, while the Calgon method addresses permanent hardness.

Answer 1

The Correct Option is B

Temporary hardness of water is primarily due to the presence of bicarbonates of calcium and magnesium.
Boiling removes temporary hardness by decomposing bicarbonates into carbonates which precipitate out.
Clark's method involves the addition of lime (Ca(OH)\(_2\)) which reacts with bicarbonates to form insoluble carbonates.
Calgon method, on the other hand, is used to remove permanent hardness, not temporary hardness.