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

Answer 1

Answer: (B), (D)

The correct options are
B $C{a}^{2+}$ ions
D $M{g}^{2+}$ 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.


$N{a}_{2}A{l}_{2}S{i}_2{O}_8.x{H}_{2}O+C{a}^{2+}\to CaA{l}_{2}S{i}_2{O}_8.x{H}_{2}O+2N{a}^{+}N{a}_{2}A{l}_{2}S{i}_2{O}_8.x{H}_{2}O+M{g}^{2+}\to MgA{l}_{2}S{i}_2{O}_8.x{H}_{2}O+2N{a}^{+}$

Hence, option (b) and (d) are correct.