For a 2-component system existing in vapor liquid equilibrium (VLE) at constant pressure= 1 atm, which of the following statements can be correct?

Question

For a 2-component system existing in vapor liquid equilibrium (VLE) at constant pressure= 1 atm, which of the following statements can be correct?

a.) T and composition can be independently varied.

b.) Choosing a T fixes the equilibrium compositions.

c.) Neither T nor composition can be varied.

d.) All of these

e.)None of thes

Answer 1

For a 2-component system (assuming that "component" means distinct molecular species, not phases) in VLE at constant pressure, the temperature will play a determinative role in the composition of both phases. This behavior tends to be covered in separations courses, and is described directly by "Txy" VLE diagrams. These Txy diagrams show the effect of temperature on 2-component phase behavior for constant pressure diagrams.

Conversely, you can hold the same system at constant temperature and change only pressure. In this case, the pressure will determine the composition of both phases. This type of behavior is described by a "Pxy" VLE diagram.