Question

How can the permanent hardness of water be removed?

• A. By addition of washing soda
• B. By addition of baking soda
• C. By boiling
• D. By addition of sodium carbonate

Answer 1

Answer: (A), (D)

The correct options are
A

By addition of washing soda

D

By addition of sodium carbonate

Permanent hardness of water is due to dissolved salts of chlorides and sulphates of calcium and magnesium which can be removed by adding sodium carbonate (Na₂CO₃) (washing soda or soda ash) which reacts with these dissolved salts to form insoluble carbonates that can be removed by filtration and then water becomes soft.