This work considers a gas mixture of uncharged monatomic and diatomic particles, which can chemically react with
each other. This process is modelled by integration of classical trajectories of the molecules. As the result one can
define the constants of dissociation and recombination, the time of vibrational relaxation as well as vibrational energy
levels distribution during the reaction. As an example the results of dissociation and vibrational relaxation simulations
for oxygen and nitrogen are presented. The reaction rates obtained from the simulations have shown sufficient
agreement with approximations of experimental data from other works.