Which of the following statements is false?

Question

A. On a xy diagram, if the y (vapor-phase composition) crosses the y = x line, the system will exhibit an azeotrope.
B. The larger the relative volatility for a binary mixture, the easier it will be (in general) to separate those two components through distillation.
C. For a system that obeys Raoult’s Law, the K-factor for a component is simply the vapor-pressure of that component divided by the system pressure.
D. The K-factors for the components in a mixture, by definition, cannot all be < 1.
E. At an azeotrope, the relative volatility for a system is, by definition, equal to 1.

Answer 1

A. Incorrect. This is true. The y = x line indicates a relative volatility of 1, which is an azeotrope.
B. Incorrect. This is true. The more “relatively” volatile one component is to the other, the easier it will be to separate (in general) via distillation.
C. Incorrect. This is true.
D. Correct. A K-factor of less than one means the component is present more in the liquid phase than the vapor phase, so this must be the case for one of the components (but not all).
E. Incorrect. This is true. The relative volatility indicates how much more volatile one component is over the other. At an azeotrope, both components are equally volatile, so the ratio of the two must be 1.