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#### Solid-Solid-Liquid Phase Diagrams: Interactive Simulations

These simulations were prepared using Mathematica. Download the free Wolfram player, and then download the simulation CDF file (link given below or click on figure to download). Try to predict the behavior when a parameter changes before using a slider to change that parameter. Screencasts below explain how to use these simulations.

##### Simulation: Solid-Solid-Liquid Equilibrium

This Demonstration shows a solid-liquid phase diagram for two elements (A and B) that also form a solid compound (A2B3); neither element A or element B is miscible in the solid phase. The amounts of each phase (solid A, solid B, compound A2B3, and a liquid phase containing A and B) are shown in the bar graph on the right. The system contains one mole total. The mole fraction of B in the liquid phase is given on the liquid bar. Change the overall mole fraction of B with the slider. Change the temperature by using the “heat added” slider, although when the black point is on the horizontal lines at 200°C and 300°C, the temperature will not change until one solid phase melts (adding heat) or the liquid phase solidifies (removing heat). The amounts of each phase present are determined from mass balances. The amount of heat added is not meant to represent the value for a real system.

Try to answer these questions before determining the answer with the simulation. We suggest that you write down the reasons for your answers.

1. At what temperatures can heat be added without a change in temperature for the binary phase diagram in the figure below?
2. If a one mole of the binary mixture represented by the diagram below is at 300 K and a mole fraction of B of 0.1 is compared to a one mole at 300 K and a mole fraction of 0.2, which composition has the higher energy or are the energies equal?