Calculate the osmotic pressure of 0.2 M aqueous solution of electrolyte at 300 K . If van't Hoff factor is $1.6\left[\mathrm{R}=0.0821 \mathrm{~atm} \mathrm{dm} \mathrm{K}^{-1} \mathrm{~mol}^{-1}\right]$.

Calculate the number of unit cells in 0.79 g metal if product of density and volume of unit cell is $1.58 \times 10^{-22} \mathrm{~g}$.

Identify secondary amine from following.

Which from following polymers is biodegradable?