[Roger]

Suppose that an iron catalyst at a particular manufacturing plant produces ammonia in the most cost-effective manner at 450 degrees C when the pressure is such that Δ_rG for the reaction 1/2 N₂ (g) + 3/2 H₂ (g) ==> NH₃ (g) is equal to -500 J mol^-1. (a) What pressure is needed? (b) Now suppose that a new catalyst is developed that is most cost-effective at 400 degrees C when the pressure gives the same value of Δ_rG. What pressure is needed when the new catalyst is used? What are the advantages of the new catalyst? Assume that (i) all gases are perfect gases or that (ii) all gases are van der Waals gases. Isotherms of Δ_rG(T, p) in the pressure range 100atm <= p <= 400atm are needed to derive the answer. (c) Do the isotherms you plotted confirm Le Chatelier's principle concerning the response of equilibrium changes in temperature and pressure?
(Thanks very much in advance!)