I've got a question that requires me to use the Van der Waals equation in the form: p(V-b)=nRT The process is isobaric, the volume changes from 1m3 to 2m3, and there is 1 mole of the unidentified gas. Ultimately, I need to find initial and final values of T. So I rearranged the formula: p(V-b)/nR=T So I need b. I think b is the volume per mole, so that's how I worked it out - as V/n. However, this gave me b as 1m3/mol and 2m3/mol. That gives me initial and final temperatures of 0K, which I'm guessing is wrong. In short, if someone could point me in the right direction as to what b actually is, I would very much appreciate it. Thank you.