The vapor liquid equilibrium relation for an ideal binary system is given by

y*${_A}$ = $\frac{\alpha{_A}{_B}x{_A}}{1 + ({\alpha}{_A}{_B} – 1)x{_A}}$

Here x${_A}$ and y*${_A}$ are the mole fractions of species A in the liquid and vapor, respectively. The relative volatility (${\alpha}{_A}{_B}$) is greater than unity.

A liquid having the composition found in the first part of the linked answer question, is flash distilled at a steady to a final liquid mole fraction of 0.25. If $\alpha{_A}{_B}$ is 2.5, the fraction of the feed vaporized is

1. 0.08
2. 0.20
3. 0.67
4. 0.74