Suppose that an intermolecular potential has a hard-sphere core of radius 'I and a shallow attractive well of uniform depth E out to a distance '2' Show, by using eqn 17.42 and the condition E« kT, that such a model is approximately consistent with a van der Waals equation of state when b« Vm, and relate the van der Waals parameters and the Joule-Thomson coefficient to the parameters in this model.