4: Chemical Potential and Equilibrium
- Page ID
- 456177
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- 4.1: Prelude to Chemical Equilibria
- The small is great, the great is small; all is in equilibrium in necessity... - Victor Hugo in “Les Miserables”
- 4.2: Chemical Potential
- Equilibrium can be understood as accruing at the composition of a reaction mixture at which the aggregate chemical potential of the products is equal to that of the reactants.
- 4.3: Activities and Fugacities
- To this point, we have mostly ignored deviations from ideal behavior. But it should be noted that thermodynamic equilibrium constants are not expressed in terms of concentrations or pressures, but rather in terms of activities and fugacities .
- 4.4: Pressure Dependence of Kp - Le Châtelier's Principle
- Since the equilibrium constant is a function of change in Gibbs energy, which is defined for a specific composition (all reactants in their standard states and at unit pressure (or fugacity), changes in pressure have no effect on equilibrium constants for a fixed temperature. However, changes in pressure can have profound effects on the compositions of equilibrium mixtures.
- 4.5: Degree of Dissociation
- Reactions such as the one in the previous example involve the dissociation of a molecule. Such reactions can be easily described in terms of the fraction of reactant molecules that actually dissociate to achieve equilibrium in a sample. This fraction is called the degree of dissociation.
- 4.6: Temperature Dependence of Equilibrium Constants - the van ’t Hoff Equation
- The value of Kp is independent of pressure, although the composition of a system at equilibrium may be very much dependent on pressure. Temperature dependence is another matter. Because the value of is dependent on temperature, the value of Kp is as well. The form of the temperature dependence can be taken from the definition of the Gibbs function.
- 4.E: Chemical Equilibria (Exercises)
- Exercises for Chapter 9 "Chemical Equilibria" in Fleming's Physical Chemistry Textmap.