The effect of chemical reaction rates on experiments of high enthalpy air in the CUBRC LENS facility is studied. Nozzle flow simulations are performed at approximately 10 MJ/kg specific enthalpy. Computational results for NO concentration are compared with experimental measurements made using laser absorption techniques. The chemical reaction rates used in these simulations were obtained from several literature sources and some are modified to be suited for the experimental conditions. Results using this reaction rate model under similar conditions are compared against simulations that employ the vibrational state-specific approach of Park. Both quasi one-dimensional and axisymmetric simulations of the flow inside a conical nozzle are presented. Our simulations agree well with those of Park, but do not reproduce the measurements made in the CUBRC LENS-I facility. We consider several more advanced chemical kinetics models and vary the reaction rates based on values from the literature. However to date, we are unable to explain the difference between the simulations and the experiments.