[crown joule]

So this is one of our homework problems, but between 12 students, we were only able to solve half of it.

#6. Derive an expression for the internal pressure of a van der Waals gas (see eqn 7.1) in terms of a, b, and Vm.  Use the expression to show that (mu) = {(2a/RT)-b}/Cp,m by using the definition of (mu) and appropriate relations between partial derivatives. (Hint: Use the approximation pVm = RT when it is justifiable to do so.)

VDW eqn:

P = (RT/V_m-b) - (a/V_m²)  b/{a(V_m-b)}

after this step, we tried to derive the rest using

(mu)_J-T = -{(dH/dP)_T}/C_p    *where d is partial derivative.

but alas, we failed.

Any suggestions or starting points for us to reach this derivative?