Question

explain by writing a word equation hard water gets softened on mixing with a solution of washing soda

Answer 1

Sodium carbonate, Na2CO3, is also known as washing soda. It can soften water that has temporary hardness and it can soften water that has permanent hardness.

Sodium carbonate is soluble in water and adds a large amount of carbonate ions to the water. These react with dissolved calcium ions, forming a precipitate of calcium carbonate:

Ca2+(aq) + CO32–(aq) → CaCO3(s)

The calcium ions come from the hard water and the carbonate ions from the washing soda.

Answer 2

calcium chloride+Sodium carbonate ➡
Calcium carbonate +Sodium chloride

CaCl2+Na2CO3 ➡CCo3+NaCl