The variation of the entropy of mixing with composition for two perfect gases at constant temperature and pressure is given by

Where x is the mole fraction of A, n is the total amount of A and B (mol), and R is the gas constant (J K^-1 mol^-1).

To graph the change in entropy (J K^-1) enter the parameter (i.e., n) and hit New Plot. Up to 5 plots can be displayed at one time. The Clear button will remove all plots. To see the parameters for each plot hit the Legend on/off button. The Redraw button will refresh the graph. This is useful when the function domain (i.e., mole fraction of A (x) ) has been changed. To see the value of each plot at a given point, move your cursor to the desired location then click and hold.