The osmotic pressure of an aqueous solution of urea (molar mass =...

Using the formula for osmotic pressure $\pi = CRT$, the molarity $C$ of the solution is calculated as follows:

$C = \dfrac{\pi}{RT} = \dfrac{0.492}{0.082 \times 300} = \dfrac{0.492}{24.6} = 0.02 \text{ mol L}^{-1}$

Mass of urea in $1 \text{ L}$ of solution $= 0.02 \text{ mol} \times 60 \text{ g mol}^{-1} = 1.2 \text{ g}$

Given the density of the solution is $1.0 \text{ g mL}^{-1}$, the mass of $1 \text{ L}$ ($1000 \text{ mL}$) of solution is $1000 \text{ g}$.

Concentration in ppm $= \dfrac{\text{Mass of solute}}{\text{Mass of solution}} \times 10^6$

Concentration in ppm $= \dfrac{1.2}{1000} \times 10^6 = 1200$

Answer: $1200$