Which among the following compounds has lowest boiling point?

Calculate the molar mass of an element if it forms fcc unit cell structure [mass of unit cell $=1.8 \times 10^{-22} \mathrm{~g}, \mathrm{~N}_{\mathrm{A}}=6.022 \times 10^{23} \mathrm{~mol}^{-1}$ ]

Calculate the osmotic pressure of 0.03 mole of non electrolyte solute dissolved in $0.1 \mathrm{dm}^3$ of water at $300 \mathrm{~K} .\left[\mathrm{R}=0.082 \mathrm{dm}^3 \mathrm{~atm} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right]$