The present work studies the non-equilibrium chemical reactions occurring in a re-entry flow with a stagnation enthalpy of 31.53 MJ/kg. The objective is to investigate the chemical and physical processes in different regions of the flowfield, and their effect on the stagnation point heat flux. Numerical experi- ments are performed by altering the reaction rates from their baseline values and the computed flowfield solutions are analyzed in detail. The primary chemical activity consists of dissociation of N and O in the shock layer, and recombination of only N atoms in the vicinity of the isothermal cold wall. The reaction mechanisms involved in the conversion of N atoms to molecules are presented and the rate limiting steps are identified. The surface heat flux is found to be most sensitive to these rate constants. Increasing their values enhances the heat transfer rate and vice versa. The study also highlights the effect of shock layer chemistry and chemical non-equilibrium on the surface predictions. Most importantly, the analysis explains why the heating rate is sensitive to some of the rate constants and relatively insensitive to other reaction rates.