Water — Question 28

Below are the balanced equations for removal of temporary & permanent hardness in water by addition of washing soda:

Permanent Hard Water:

$\underset{\text{Washing soda}}{\text{Na}_2\text{CO}_3} + \underset{\text{Calcium sulphate}}{\text{CaSO}_4} \longrightarrow \underset{\text{Calcium carbonate}}{\text{CaCO}_3↓} + \text{Na}_2\text{SO}_4$

Temporary Hard Water:

$\underset{\text{Washing soda}}{\text{Na}_2\text{CO}_3} + \underset{\text{Calcium bicarbonate}}{\text{Ca(HCO}_3)_2}\longrightarrow \underset{\text{Calcium carbonate}}{\text{CaCO}_3↓} + 2\text{NaHCO}_3$