Ammonia atmospheric thermodynamic equilibrium

Nitrogen, N2, is very unreactive. The Haber process is the economically important industrial process by which atmospheric N2 is converted to ammonia, NH3, a soluble, reactive compound. Innumerable dyes, plastics, explosives, fertilizers, and synthetic fibers are made from ammonia. The Haber process provides insight into kinetic and thermodynamic factors that influence reaction rates and the positions of equilibria. In this process the reaction between N2 and H2 to produce NH3 is never allowed to reach equilibrium, but moves toward it. 

From a thermodynamic model [396] of the chemisorption of H2 we have found that under an equilibrium pressure of 1 atmosphere, the coverage by H decreases from 1 at 500 K to 0.15 at 1000 K. By calculating the outcome of a volumetric chemisorption experiment from a model of the kinetics of ammonia synthesis [396], it is concluded that H is by far too weakly adsorbed to be used in a titration of the number of active sites on the catalyst surface. 

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