The Osmotic pressure of solution containing 4.0g of solute (molar mass 246) per litre at 27°C is
(R = 0.082L atm k^–1 mol^–1)

$\mathrm{\pi }=\mathrm{CRT}$

Where, π= Osmotic pressure

V=volume=1 lit

R= gas constant =0.0821K⁻¹mole⁻¹ ; T= Temperature =273+27=300k

Given, mass of solute=4g and molar mass = 246g

$\mathrm{\pi }=\frac{\mathrm{n}}{\mathrm{V}}\mathrm{RT}=\frac{4}{246}\times 0.0821\times 300=0.4\mathrm{atm}.$