Answer 1

Removal of hardness of permanent hardness of water—
By Adding sodium carbonate (washing soda)
Permanent hardness of water is removed when water is treated with a small quantity of sodium carbonate.
It reacts with the soluble chlorides and sulphates of calcium and magnesium to form their insoluble carbonates. These can be removed by filtration and then the water becomes soft. Sodium sulphate or sodium chloride formed after the reaction does not affect the soap.

\[\ce{\underset{\text{(sodium carbonate)}}{Na2CO3}+ \underset{\text{(calcium sulphate)}}{CaSO4}→\underset{\text{(insoluble calcium carbonate)}}{Na2SO4}}\]