ENGR-1100 Introduction to Engineering Analysis

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Lecture 16 Classical Thermodynamics of
Multicomponent Systems

• Activity
• Partial molar quantities
• Calculations of partial molars from total
  quantities
• Problems

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Activity
Defining Upon integration Where is
arbitrary and typically taken as of a pure
component at a temperature of interest
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Ideal gas activity
Chemical potential of an ideal gas Where Pi
is the partial pressure of ith component
Where is arbitrary and typically taken as
the pressure over the pure condensed phase o the
species i. With this choice
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Partial Molar Properties
Total Gibbs free energy On the molar
bases Where is the partial molar Gibbs
free energy
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Partial Molar Properties II
From and
Where the derivative is with respect to
number of moles, not atoms or molecules Similarly
for volume
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Partial Molar Properties III
Other relations And similar
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Calculating partial properties from total
For a two component system Since With
and
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Problem 18.5
The molar Gibbs free energy of a binary system at
a particular temperature and pressure is given by
Calculate the partial molar Gibbs free
energies for A and B at a composition of XB
0.3