# The molecular formula of a commercial resin used for exchanging ions in water softening is "C"_8"H"_7("SO"_3)"Na" molecular weight 206. The maximum uptake of "Ca"^(2+) ions by the resin when expressed in mole per gram resin is?

Sep 9, 2017

Balanced equation for water softening can be written as

$2 {\text{C"_8"H"_7("SO"_3)"Na"+"Ca"^(2+)->("C"_8"H"_7("SO"_3))_2"Ca"+2"Na}}^{+}$

From the equation we see that $2$ moles of resin require $1$ mole of ${\text{Ca}}^{2 +}$

Given is molecular weight of resin $= 206$.
$412$ g of resin require $1$ mole of ${\text{Ca}}^{2 +}$
$\therefore$ Maximum uptake of ${\text{Ca}}^{2 +}$ is $= \frac{1}{412}$

$\approx 0.0024$ moles/g of resin