Calculate the number of unit cells in $1\text{cm}^3$ of metal if it forms simple cubic structure with unit cell edge length 500 pm.

Which of the following concentrations of solutions of urea in water exhibits minimum freezing point depression?

Calculate van't Hoff factor for aqueous solution of 0.02 m formic acid if it freezes at -0.045 $^\circ\text{C}$.
[ $K_f$ = 1.86 K kg $\text{mol}^{-1}$ and freezing point of water = $0\ ^\circ\text{C}$ ]

Calculate the molar mass of nonvolatile solute when 4 g of it is dissolved in 100 g solvent that boils at 319.4 K [$K_b$ = 2.4 K kg $\text{mol}^{-1}$; B.P of pure solvent = 319 K]