Question

For an ideal binary liquid solution with $P_A^{\circ }>P_B^{\circ }$, which relation between $X_A$ (mole fraction of A in liquid phase) and $Y_A$ (mole fraction of A in vapour phase) is correct?

• A. $Y_A<Y_B$
• B. $X_A>X_B$
• C. $\frac{Y_A}{Y_B}>\frac{X_A}{X_B}$
• D. $\frac{T_A}{Y_B}<\frac{X_A}{X_B}$

Answer 1

Answer: (C)

$\frac{Y_A}{Y_B}>\frac{X_A}{X_B}$

Since, $P_A^{\circ }>P_B^{\circ }$, A is more volatile than B.

Hence, the ratio of the number of moles of A in vapour state to the number of moles of A in the liquid state will be greater than the ratio of the number of moles of B in a vapour state to the number of moles of B in the liquid state.
The ratio of mole fraction of A in vapour state to the mole fraction of A in the liquid state will be greater than the ratio of mole fraction of B in a vapour state to the mole fraction of B in the liquid state

Thus, $\frac{Y_A}{X_A}>\frac{Y_B}{X_B}$ or $\frac{Y_A}{Y_B}>\frac{X_A}{X_B}$.

Hence, the correct option is $C$