Chemistry - Hydrogen and Its compound Question with Solution | TestHub

Temparoy hardness is because of magnesium calcium hydrogen carbonates that can be removed by boilling.

When the soluble salt of magnesium and calcium are present in the form of chlorides and sulphides, we call it permanent hardness because this hardness cannot be removed by boilling.

To remove Permanent Hardness of Water:

Gan’s Permutit Method:

In this method, sodium aluminium ortho silicate, known as permutit or zeolite, is used to remove the permanent hardness of the water.

Reaction:  Na₂ Al₂Si₂O 8.KH₂O + Ca++→ 2Na⁺ + Ca Al₂Si₂ O 8.xH₂O

Calgon’s Process:

In this method, sodium-hexa-meta-phosphate (NaPO3)6 known as Calgon, is used. The hardness in water is removed by the adsorption of Ca⁺⁺ and Mg⁺⁺ ions.

Ion Exchange Resin Method:

In this method, the permanent hardness of water is removed by using resins. Ca⁺⁺ /Mg⁺⁺ ions are exchanged with Cl^-, and SO₄^2- ions are exchanged with anion exchange resin (RNH₂OH). Demineralised water is formed in this process.

⇒ 2RCOOH + Ca⁺⁺ → (RCOO)₂Ca + 2H⁺

⇒ RNH₂OH + Cl- → RNH₂Cl + OH-

⇒ H⁺ + OH^- → H₂O