What is the total number of adjacent unit cells shared by each face particle of fcc unit cell ?

A metal forms fcc structure. Calculate the volume of fcc unit cell in $\text{cm}^3$ if void volume is $1.66 \times 10^{-23}\ \text{cm}^3$.

Calculate the mole fraction of solute in solution if vapour pressure of a solution and pure solvent are 27 mm Hg and 30 mm Hg respectively at 298 K.

Calculate the molar mass of nonelectrolyte solute when 6 gram of it is dissolved in 1 $\text{dm}^3$ water has osmotic pressure $2.4\ \text{atm}$ at 300 K $(R = 0.0821\ \text{atm dm}^3\ \text{K}^{-1}\ \text{mol}^{-1})$