Chapter 2.6, Problem 37P

Using the Same method as in the text, calculate the entropy of mixing for a system of two monatomic ideal gases, A and B, whose relative proportion is arbitrary. Let N be the total number of molecules and let x be the fraction of these that are of species B. You should find $\Delta S_{mixing}=-NK\left[x\ln x+\left(1-x\right)\ln \left(1-x\right)\right]$.

Check that this expression reduces to the one given in the text when $x=\text{1/2}$.