Answer. Sodium zeolite is a naturally occurring resin of sodium aluminum silicate NaAl (Si03)2, which can also be prepare artificially. It is used for softening of water at domestic as well as on; industrial scale. When water is passed through resin sodium ions o the resin are exchanged with the unwanted calcium and magnesium; ions of the hard water as shown in figure:
Ion exchange for removal of hard water ions
Na2 zeolite + CaSO4(aq) ———> Ca zeolite + Na2SO4(aq)