Suppose that a gas obeys the modified van der Waals equation P(Vm-b)=RT, and that b has a value of 0.0200 dm^3 mol^-1. If 0.500 mol of the gas is reversibly compressed from an initial volume of 2.00 dm^3 to a final volume of 0.500 dm^3 how much work is done on the system? How much work would have been done if the gas were ideal? Account for the differences the two values.