The effect of confinement on chemical equilibria is investigated within the framework of a density functional theory for chemical reactions in slit pores in equilibrium with a bulk reservoir. Factors like pore size, temperature, bulk pressure, external field, and capillary condensation are known to have considerable impact on the phase equilibria of a confined system. We analyze the impact of these factors on the composition (hence conversion) of a model reacting system, from a chemical equilibria perspective. Canonical Monte Carlo simulations are performed to compare with the theoretical findings for the spatial distribution of the reactants and products in the pore. Enhanced adsorption leads to significantly higher conversions in reactions occurring in the pore phase than in the bulk phase. The validity of this framework for reacting systems is then further tested on a real system, viz., dimerization of nitric oxide in graphite micropores (size <3 nm). The results obtained are in very good agreement with the reactive Monte Carlo simulations results reported for the same system by Turner, Johnson, and Gubbins [J. Chem. Phys. 114, 1851 (2001)]. (C) 2003 American Institute of Physics.