Question

Temporary and permanent hardness of water can be removed by:-

• A. For temporary hardness:- ${\text{Na}}_2{\text{CO}}_3$ For permanent hardness:- ${\text{Ca(OH)}}_2$
• B. For temporary hardness:- ${\text{Ca(OH)}}_2$ For permanent hardness:- Boiling
• C. For temporary hardness:- Boiling For permanent hardness:- ${\text{Ca(OH)}}_2$
• D. For temporary hardness:- Boiling For permanent hardness:- ${\text{Na}}_2{\text{CO}}_3$

Answer 1

The correct option is D

For temporary hardness:- Boiling

For permanent hardness:- ${\text{Na}}_2{\text{CO}}_3$

Temporary hardness of water is due to the presence of dissolved bicarbonates of calcium and magnesium. This can be removed by boiling or addition of calcium hydroxide ${\text{Ca(OH)}}_2$.

Permanent hardness of water is due the presence of dissolved sulphates and chlorides of magnesium and calcium. This can be removed by addition of washing soda $\left({\text{Na}}_2{\text{CO}}_3\right)$.