The molecular formula of a commercial resin used for exchanging ions in water softening is C₈H₇SO₃Na (Mol. wt. 206). What would be the maximum uptake of Ca²⁺ ions by the resin when expressed in mole per gram resin?

According to the reaction of ion exchange resin: 2 8 7 3 8 7 3 2 2 (2 ) ( ) C H SO Na mol Ca C H SO → (1 ) 2 Ca mol Na i.e., 2 moles of resin are required to replace 1 mole of calcium ions and 206 2 412g x resin required for the uptake of 1 mole of calcium ions. Therefore, 1/ 412mol of calcium are replaced by 1 gram of resin.