Osmotic Pressure and Concentration of Solution

For very dilute solutions, the osmotic pressure follows the equation

where $V$ is the volume of the solution in $\mathrm{dm^3}$ containing $n_2$ moles of nonvolatile solute, $R$ is the gas constant equal to $0.08206\ \mathrm{dm^3\,atm\,K^{-1}\,mol^{-1}}$, and $\pi$ is the osmotic pressure in atm.

The term $n_2/V$ is the concentration in molarity ($M$). Eq. (2.19) thus can be written as

$\pi = M R T \qquad \text{...(2.20)}$ …