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Unformatted text preview: PHYS 333 Winter 2009 Assignment 4 Due: 5:00 pm Friday January 30 Most of these problems are from Schroeder’s book. 1. Entropy of Mixing. Calculate the increase in entropy when two different ideal gases diffuse into each other. The two gases are originally in separate containers, but with the same pressure and temperature. There are N A molecules of gas A, and N B molecules of gas B, with N = N A + N B , occupying volumes V A and V B respectively. After they have mixed, their volume is V = V A + V B . Do the calculation in three independent ways, and show, each time, that the answer is Δ S = k B N A ln[ N/N A ] + k B N B ln[ N/N B ] (a) Take the Sackur-Tetrode expression for the entropy, and calculate the change directly. (b) Schroeder, 2.38. Without using the S-T expression, show that the entropy change corre- sponding to mixing any two substances (think of two Einstein solids, for example) must be k B ln[ N ! /N A ! N B !]. Show that this is the same expression....
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This note was uploaded on 04/11/2010 for the course PHYS 333 taught by Professor Harris during the Winter '09 term at McGill.
- Winter '09