The vapour pressure of $A$ and $B$ at $27^{\circ} \mathrm{C}$ are 60 mm Hg and 40 mm Hg respectively

Question

The vapour pressure of $A$ and $B$ at $27^{\circ} \mathrm{C}$ are 60 mm Hg and 40 mm Hg respectively. If $A$ and $B$ are mixed such that the mole fraction of $A$ in the mixture is 0.8 , then the mole of $B$ in the vapour phase is $\mathrm{Z} 	imes 10^{-1}$. The value of Z is

Professor PC Thomas Classes · Answer

Raoult's Law: $P_T = X_A P_A^0 + X_B P_B^0$.