Physical Chemistry I
Focus Questions
Canonical Partition Function

22.2 (skip pp. 826 - 833)

1.    The observed pressure of a system is a time average over the impacts of individual molecules on the walls.  When we did our statistical development, we looked at all the possible distributions that might occur. . . ever.  This description says let's look at a system for one microsecond and see what its distribution is.  In our statistical development, we fixed only the total energy of the system.  We developed what is called the molecular partition function.  Our ensemble is all the possible microstates with the defined energy (4hn, or 5hn).  This section introduces the idea of a canonical ensemble.  For a canonical ensemble, volume (V), temperature (T), and composition (N) are fixed.  Energy is not fixed.  The canonical ensemble is best exemplified by the sentence immediately following equation 22.1

2.    What does the word 'canonical' mean?  How is a canonical partition function different from the partition function we defined?  (other than the use of a capital 'Z')

skip the section "Evaluation of p^", resume reading at equation 22.15

3.    Why the letter 'Z'?

pp. 834 - 836, start with the top line ". . .the system's energy . . "

4.    Why can we multiply separate partition functions to obtain the total partition function?

5.    List the restrictions identified in equation 22.46.  How is equation 22.49 different?  What restriction is removed?

6.    Under what systemic conditions are particles distinguishable?  When are particles indistinguishable?

Calculating Energy and Entropy:  

p. 849 - 854

read for review.