Question

Demineralised water is obtained by-

• A. Boiling
• B. Treating with calgon
• C. Ion exchange resins
• D. All of these

Answer 1

The correct option is C

Ion exchange resins

Water which is free from all soluble minerals salts is called as demineralised water. Demineralised water is obtained by passing water successively through a cation exchanger and an anion exchange resins. In cation exchanger $C{a}^{2+},M{g}^{2+},N{a}^{+}$ and other cations present are removed by exchanging them with $H^{+}$ ions while in anion exchanger $C{l}^{-},HC{O}^{-3},S{O}_4^{2-}$ present in water are removed by exchanging them with $o{h}^{-}$ ions

$h^{+}$ (released in cation exchanger) + $O{H}^{-}$( released in anion exchanger) $\to H_{2}O$