Nonequilibrium channel flow is analyzed for an arbitrary mixture of monatomic and diatomic gases with the assumption that the chemical and vibrational rate processes are not coupled. A new numerical formulation permits precise evaluation of the chemical and physical properties of the mixture in all regions of the flow. The special case of high enthalpy airflow in a hypersonic nozzle is examined, and a comparison is made with earlier results which use approximate equations in the near‐equilibrium region of the flow. The comparison shows that when chemical rates are accurately known in this region, the description of the chemical nature of the flow in downstream regions is altered.