Partial Molar Quantities: Summary
Key points from this module:
- Partial molar quantities are properties assigned to a component in a mixture, even though the components are mixed on a molecular scale.
- In general, partial molar quantities do not equal molar quantities.
- The partial molar Gibbs free energy for a component in a mixture is the chemical potential for that component.
- For an ideal solution, the partial molar enthalpy is the molar enthalpy, but the partial molar entropy does not equal the molar entropy because the entropy of mixing is not zero for an ideal solution.
- As the mole fraction of a component approaches one, its partial molar quantity approaches its molar quantity.
- For a plot of partial molar quantity versus mole fraction for a binary mixture, the partial molar quantities are the intercepts at x1 = 0 and 1 for a line drawn tangent to the plot at the mole fraction of the mixture.
From studying this module, you should now be able to:
- Explain the physical meaning of a partial molar quantity.
- Determine the partial molar quantities for a binary mixture, given a plot of the mixture property as a function of mole fraction.
- Given an analytical expression for the mixture property as a function of mole fractions, be able to calculate partial molar quantities.
- Determine the excess molar property for a binary mixture, given a plot of the mixture property as a function of mole fraction.
- Calculate a mixture property at a given composition from its partial molar quantities.
Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder