Explain with equation, what is noticed when permanent hard water is treated with

(a) slaked lime

(b) washing soda

(a) In order to treat permanent hard water, slaked lime is used, magnesium hydroxide and calcium carbonate precipitates out and can be easily filtered.

MgSO₄ + Na₂CO₃ + Ca(OH)₂ ⟶ Mg(OH)₂ ↓ + CaCO₃ ↓ + Na₂SO₄

(b) Washing soda is added to hard water, which results in settling down of insoluble carbonates which can be removed by filtration.

$\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

$\underset{\text{Washing soda}}{\text{Na}$2\text{CO}3} + \underset{\text{Calcium chloride}}{\text{CaCl}2} \longrightarrow \underset{\text{Calcium carbonate}}{\text{CaCO}3↓} + 2\text{NaCl}