A solution is prepared by dissolving 17.1 g of sucrose to make 1000 mL of solution in water. The osmotic pressure of the solution at 20 °C is :

Wt. of solute(sucrose) ${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}={\mathrm{W}}_2$

$=17.1\mathrm{g}$; volume of solution $=1000\mathrm{mL}\times \frac{1\mathrm{L}}{1000\mathrm{mL}}=1\mathrm{L}$

$\mathrm{R}=0.0821 \mathrm{L}$ atm ${\mathrm{K}}^{-} {\mathrm{mol}}^{-}; \mathrm{T}=20+273=293\mathrm{K};$

mol wt. of ${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}=(12\times 12)+(22\times 1)+(11\times 16)=342 \mathrm{g} {\mathrm{mol}}^{-}={\mathrm{M}}_2$

Osmotic pressure, 

$\begin{array}{l}\mathrm{\pi }=\frac{{\mathrm{W}}_2}{{\mathrm{M}}_2\mathrm{V}}\times \mathrm{RT}\\ =\frac{17.1 \mathrm{g} \times 0.0821 \mathrm{L} \mathrm{atm} {\mathrm{K}}^{-}{\mathrm{mol}}^{-} \times 293 \mathrm{K}}{342 \mathrm{g} {\mathrm{mol}}^{-} \times 1 \mathrm{L}}\end{array}$

$\therefore$     $\mathrm{\pi }=1.203$ atm.