sudden removal partition initial equil state final equil state Figure 2: For Problem 4 Fig. 2 shows a 'toy-model' version of the perfect gas situation in Problem 3. The left and right volumes are still equal; both consist of four 'cells'; each cell can hold one molecule(black circle). The initial and final equilibrium states have a multiplicity of microstates 2 = M!/N!(M N)!, corresponding to the # of ways we can stuff N molecules into M accessible cells. (a) Give the microstate multiplicities for the initial and final equilibrium states: ini, and fin- (b) Use S = kg In 12, to explain how the change in multiplicity gives a microscopic explanation that is consistent with your answer to Prob. 3