The concentration of IL of $\mathrm{CaCO}_3$ solution is 1000 ppm . What is its concentration in…
The concentration of IL of $\mathrm{CaCO}_3$ solution is 1000 ppm . What is its concentration in $\mathrm{mol} \mathrm{L}^{-1}$ ?
$(\mathrm{Ca}=40 \mathrm{u}, \mathrm{O}=16 \mathrm{u}, \mathrm{C}=12 \mathrm{u})$
$10^{-3}$
$10^{-1}$
$10^{-4}$
$10^{-2}$
Solution
$\mathrm{ppm}($ parts per million $)=\frac{\mathrm{mg} \text { of solute }}{\mathrm{L} \text { of solution }}$
Given,
$\mathrm{ppm}=1000$
$\begin{aligned} & \text { volume }=1 \mathrm{~L} \\ & \mathrm{mg} \text { of solute }=\mathrm{ppm} \times \mathrm{L} \text { of solution } \\ & =10^3 \times 1 \\ & \text { weight of solute }=10^3 \mathrm{mg}\end{aligned}$
$\begin{aligned} & \text { Concentration }=\frac{\text { no. of moles }}{\text { volume }} \\ & \text { no. of moles }=\frac{\text { weight of solute }}{\text { molecular weight of solute }}\end{aligned}$
$\begin{aligned} & =\frac{10^3 \times 10^{-3} \mathrm{~g}}{100 \mathrm{~g} \mathrm{~mol}^{-1}}\left[1 \mathrm{mg}=10^{-3} \mathrm{~g}\right] \\ & =10^{-2} \mathrm{~mol}\end{aligned}$
Concentration (c) $=\frac{10^{-2} \mathrm{~mol}}{1 \mathrm{~L}}=10^{-2} \mathrm{~mol} \mathrm{~L}^{-1}$