The aim of this work is the numerical solution of laminar flows over a flat wall perturbed by mixing and temperature increase due to a chemical reaction. The model approximates the overall, single step, binary, irreversible reaction between two species, resulting a third, which is taken to be a process of first order with respect to each of the reactants, being the specific reaction rate controlled by temperature-dependent Arrhenius kinetics. The simulations are performed using the finite differences explicit Runge-Kutta three-stages scheme for second order time and space approximations. Consistent results, for reactant and product concentration fields, as well as for temperature of reaction, are obtained, showing that the model is able to follow nonlinear behavior of the mixing and reaction progress, for Schmidt and Prandtl numbers of order 1, Zel'dovich 1, Damkohler 300 and heat release parameter 1, which are values for gaseous hydrocarbon chemistry. Besides, it is worth pointing out that these results build on earlier ones, which were obtained from thin-layer model approximations.