This Demonstration shows the phase equilibrium for a binary system of two partially miscible liquids, A and B. Because of the partial miscibility, vapor-liquid equilibrium (VLE), liquid-liquid equilibrium (LLE), and vapor-liquid-liquid equilibrium (VLLE) are present on the phase diagram. You can vary the mole fraction of component B and the heat added (location of the black dot). The heat added changes the temperature, except when at 77
C, where all three phases are in equilibrium:
), and vapor (
). At this temperature, one phase must completely evaporate (or condense if removing heat) before the temperature increases (or decreases). The amount of heat added is used to illustrate the system behavior and to show how at 77
C all three phases exist. The relative amounts of each phase are determined from the lever rule (mole balance) and shown in the bar graph. The mole fraction(s) of component B in each phase are also displayed on the bar graph, for the phases present. In the multiple phase regions, dashed lines in the
diagram show what the mole fraction of B is where the vertical lines cross the x-axis.