Phase Equilibria I Problem Formulation

To demonstrate mastery of the material in Chapter 6, you should be able to  

Identify the role of the chemical potential—that is, the partial molar Gibbs energy—as the chemical criteria for equilibrium. 

So far, we have used thermodynamics to form relationships between the states of a system that undergoes certain processes. We can apply the first and second law to both reversible and irreversible processes to get information about (1) how much power is needed 

These problems lead to the second major branch of thermodynamics, which we will now formulate. It deals only with equilibrium systems. It should be pointed out that this branch still uses the same observations of nature (conservation of energy and directionality) that we have already studied. In these problems, however, we wish to calculate how species distribute among phases when more than one phase is present (phase equilibria) or what types of species are formed and how much of each type is produced as systems approach equilibrium when the molecules in the system chemically react (chemical reaction equilibria). We will consider phase equilibria first. These calculations are restricted to equilibrium systems therefore, they give information on the direction of the driving force for a given system (i.e., the system will spontaneously move toward its equilibrium state) but no information on the rate at which it will reach equilibrium. 

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