The Boltzmann equation for reacting and diffusing components of binary mixture is solved by means of the perturbative Chapman-Enskog method. It is assumed that all molecules have identical mechanical properties and the system is in mechanical equilibrium. Typical reaction schemes consisting of bimolecular processes only are considered. Corrections of two orders to the distribution functions perturbed by the chemical reactions are calculated. The first-order correction gives a modification of the reaction rate in the reaction-diffusion equation for concentrations. The correction to the diffusion coefficient is obtained in the second-order approximation. Moreover, the solution at this order yields a term proportional to the square of the concentration gradient. These corrections are calculated for the molecular model of reactive hard spheres. For low activation energies the magnitude of the relative correction to the diffusion coefficient can be larger than that to the reaction rate.