Chemistry - Liquid Solution Question with Solution | TestHub

The osmotic pressure $\pi$ is given by the formula:

$\pi =\frac{WRT}{MV}$

Where $W$ is the mass of the solute, $R$ is the gas constant, $T$ is the temperature, $M$ is the molar mass of the solute, and $V$ is the volume of the solution in liters (or ${\text{dm}}^3$).

Rearranging the formula to solve for $M$:

$M=\frac{WRT}{\pi V}$

Substituting the given values ($W=1.6$ g, $R=0.082$ ${\text{dm}}^3{\text{ atm K}}^{-1}{\text{mol}}^{-1}$, $T=298$ K, $\pi =0.2$ atm, $V=600$ mL $=0.6$ ${\text{dm}}^3$):

$M=\frac{1.6\times 0.082\times 298}{0.2\times 0.6}$

$M=\frac{39.0976}{0.12}$

$M=325.81$ ${\text{g mol}}^{-1}$

Rounding to one decimal place, we get $325.8$ ${\text{g mol}}^{-1}$.