Question

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8H_7SO_3Na$ (molecular weight = $206$). What would be the maximum uptake of $Ca^{2+}$ ions by the resin when expressed in mole per gram resin

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

Answer 1

Answer: (D)

$\frac{1}{412}$

Answer 2

$\underset{2 \,{\text{mole}}}{2 C _{8} H _{7}} SO _{3} Na + \underset{1 \,{\text{mole}}}{Ca ^{7+}} \longrightarrow\left( C _{8} H _{7} SO _{3}\right)_{2} Ca$
$2 \times 206\, gm$ take $1$ mole of $Ca ^{2+}$
$\therefore 1\, gm$ takes $\frac{1}{412}$ mole of $Ca ^{2+}$.