1. The problem statement, all variables and given/known data I have a system u =Av-2exp(s/R) N moles of this substance initially at T0 and P0 are expanded isentropically until the pressure is halved. What is the final temperature? 2. Relevant equations du = [tex]\partial[/tex]u[tex]\partial[/tex]s ds + [tex]\partial[/tex]u[tex]\partial[/tex]v dv du = Tds - Pdv 3. The attempt at a solution If this function is changing isentropically, ds would have to be zero, correct? The derivative of v would have to be such as to multiply P times 1/2, correct? But, if ds --> zero, how do I find my final temperature as a multiple of my initial temperature? Do I have to start plugging values which would satisfy these conditions back into the original equation?