Question

When zeolite, which is hydrated sodium aluminium silicate, is treated with hard water, the sodium ions are exchanged with :

• A. $H^{+}$ ions.
• B. $C{a}^{2+}$ ions.
• C. $S{O}_4^{2-}$ ions.
• D. $M{g}^{2+}$ ions.
• E. $O{H}^{-}$ ions.

Answer 1

Answer: (B), (D)

$C{a}^{2+}$ ions.
$M{g}^{2+}$ ions.

Permutit or zeolites are packed in a suitable container and a slow stream of hard water is passed through this material. As a result, calcium and magnesium ions present in hard water are exchanged with sodium ions in the permutit (Na+Al-Silicate). The outgoing water contains sodium salts, which do not cause hardness.

$CaC{l}_2+2N{a}^{+}\to Ca(Al-silicate{)}_2+2NaCl$

$MgC{l}_2+2N{a}^{+}\to Ca(Al-silicate{)}_2+2MgCl$

So here the sodium ions are exchanged with both $C{a}^{2+}$ and $M{g}^{2+}$ ions.

Hence options B & D are correct.