Question

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8{H}_{7}S{O}_3$ (Mol. wt. 206). Water would be the maximum uptake of $C{a}^{2+}$ ions by the resin when expressed _____ in mole per gram of resin.

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

Answer 1

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

The chemical reaction for softening water can be given as:-

$2C_8{H}_7\left(S{O}_3\right)Na+C{a}^{+2}⟶\left[C_8{H}_7\right(S{O}_3){]}_{2}Ca+2N{a}^{+}$

$\therefore$ $2$ moles of resin$\equiv 1$ mole of $C{a}^{2+}$

$\therefore$ Mass of resin = $206\times 2=412g$

For $412g$ of resin, $1$ mole of $C{a}^{2+}$ is required.

$\therefore$ Maximum uptake of $C{a}^{2+}$ ions $=\frac{1}{412}$ mole/gram of resin.