The graph on the right shows the temperaturecomposition diag

The graph on the right shows the temperature-composition diagram for a mixture of liquids A + B. Explain what type of mixture this represents. What happens to the boiling point curve when the pressure is reduced? Why do you think this occurs? How can this concept be used in separating one of the components in its pure form in a distillation process?

Solution

1) This curve represents azeotropic mixture.

2) As the pressure reduces boiling point of pure substance goes on decreasing. So the boiling point curve shifts downwords.The relative volatilities increases with reducing pressure therefore loop curve goes on spreding.

3) The mixture is deviated from Raoult Law.It is showing positive deviation from Raoults law. The azeotropic mixture boils at minimum boiling temperature where the boiling point of azeotropic mixture is less than the indivisual boiling point of componants.

4) At reduced pressure relative volatility goes on increasing, so by using this concept we can break the azeotropic point. As the pressure reduces the loop of curve(orange shaded region) goes on spreading.Once the azeotropic point break , the distillation of mixture is possible at that reduced pressure.