Question

for a van der waals gas, phi (At constant T)= a / Vmolar^2. calculate change of U molar for the isothermal reversible expansion of Nitrogen gas from an initial Volume of 1 L to 24.8 L at 298 K.what are the values of q and w?

Answer 1

If you've got the conventional vdW gas, then you can find the fundamental equation on Wikipedia here:

http://en.wikipedia.org/wiki/Van_der_Waals_equation

That will let you calculate dU. You can calculate w by integrating -p(V) dV from the initial to the final volumes, where p(V) is the equation of state (the equation for p as a function of V). Then you can subtract w from dU to get q.