The equilibrium constant Kc expression for a given chemical reaction relates the concentrations of the reactants and products at equilibrium. For the reaction:2 SO2 g + O2 g 2 SO3 g The Kc expression can be written as:Kc = [SO3]^2 / [SO2]^2 * [O2] where [SO3], [SO2], and [O2] represent the equilibrium concentrations of SO3, SO2, and O2, respectively. The exponents correspond to the stoichiometric coefficients in the balanced chemical equation.