Question

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8{H}_{7}S{O}_{3}Na$ (Mol. wt. 206). What would be the maximum uptake $C{a}^{2+}$ ions by the resin when expressed in mole per gram resin?

• A. $\frac{1}{412}$
• B. $\frac{1}{103}$
• C. $\frac{1}{206}$
• D. $\frac{2}{309}$

Answer 1

The correct option is A $\frac{1}{412}$

The maximum uptake of $C{a}^{+2}$ ion in grams per resin is:

$\underset{2\times 206g}{\underset{or}{\underset{2mol}{2C_8{H}_{7}S{O}_{3}Na}}}+\underset{1mol}{C{a}^{2+}}\to (C_8{H}_{7}S{O}_3{)}_{2}Ca+2N{a}^{+}$

From the above reaction, it can be observed that 2 moles of resin take up 1 mole of Ca.

i.e 206 x 2 g = 412 g of resin takes up 1 mole of Ca.

Number of moles of $C{a}^{2+}$ removed by one gram resin $=\frac{1}{412}mol$

Hence, option $A$ is correct.