Question

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

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

Answer 1

Answer: (B)

When zeolite (hydrated sodium aluminium silicate) is treated with hard water, sodium ions are exchanged with $C{a}^{2+}$ ions. This removes the hardness of the water.

$N{a}_{2}O.A{l}_2{O}_3.nSi{O}_2.m{H}_{2}O+CaS{O}_4\rightleftharpoons CaO.A{l}_2{O}_3.nSi{O}_2.m{H}_{2}O+N{a}_{2}S{O}_4$

Thus, zeolites act as water softeners.