Kinetic theory of a chemically reacting gas with inelastic transitions

The problem of a gas mixture of four multilevel molecules undergoing a reve rsible bimolecular chemical reaction plus mechanical encounters, leading to elastic or inelastic scattering, is addressed in the frame of extended kin etic theory. When elastic scattering is the dominant microscopic interactio n, an approximate closed set of moment equations is derived for the evoluti on of the macroscopic observables in a suitable asymptotic limit. It is sho wn that the resulting set of PDE's describes correctly the main features of the original integrodifferential kinetic equations, namely conservation eq uations, equilibria (mass action law), and H-theorem.