Calculate the osmotic pressure of 0.5 M aqueous solution of nonvolatile solute at $300 \mathrm{~K}\left[\mathrm{R}=0.0821 \mathrm{~atm~} \mathrm{dm}^3 \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right]$

The osmotic pressure is determined using the van't Hoff equation: $\Pi = iCRT$.

Given a $0.5\ \mathrm{M}$ non-electrolyte solution at $300\ \mathrm{K}$, the van't Hoff factor is $i = 1$. Substituting $C = 0.5$, $R = 0.0821$, and $T = 300$ yields $\Pi = 1 \times 0.5 \times 0.0821 \times 300$.

This simplifies to $\Pi = 12.315\ \mathrm{atm}$, or $12.32\ \mathrm{atm}$ when rounded.

The value matches option B.