1. The problem statement, all variables and given/known data It's just that in my textbook, for section titled "Second virial coefficients can be used to determine intermolecular potentials," I have an equation that I do NOT understand how it was derived---I tried to do it over and over, but couldn't quite figure how. If anyone could explain, thank you!!! B2v(T) = RT * B2p(T), where B2v(T) and B2p(T) are virial coefficient 2. Relevant equations B2v(T) = RT * B2p(T), where B2v(T) and B2p(T) are virial coefficient 3. The attempt at a solution I assume the equation comes from Z, the compressibility factor: Z = PV/RT, where it can be expanded to: Z = 1 + B2v(T)/V + B3v(T)/V2 + ... Z = 1 + B2p(T)*P + B3p(T)*P2 + ... So, I equivocated 1 + B2v(T)/V + ... = 1 + B2p(T)P + ... B2v(T)/V + ... = B2p(T)P + ... ...and tried multiplying both side by V or divide by P to cancel out other virial coefficients with numbers larger than 2 (meaning B3v and B3p), but I don't know how to progress anymore.......pls give me hints! I want to understand how the original equation B2v(T) = RT * B2p(T) was obtained!