The vapour pressure of a pure liquid $A$ is 70 torr at 300 K . It forms an ideal solution with another liquid $B$. The mole fraction of $B$ is 0.2 and total vapour pressure of the solution is 84 torr at the same temperature. The vapour pressure of pure liquid $B$ (in torr) is

If 2 g of NaOH is dissolved to make 200 mL solution at $25^{\circ} \mathrm{C}$, the molarity ( $M$ ) at $90^{\circ} \mathrm{C}$ is

A solvent freezes at $17^{\circ} \mathrm{C}$ and its latent heat of fusion is $180 \mathrm{Jg}^{-1}$. The molal depression constant of the solvent is [units of $K_f=\mathrm{K} \mathrm{kg} \mathrm{mol}^{-1}$ ]

A liquid mixture is an ideal solution, if

(A) it obeys ideal gas equation

(B) it obeys Raoult's law at all concentrations

(C) solute - solute, solute - solvent and solvent solvent interactions are similar