The equilibrium constant Kc expression for the given chemical equation 2NO2 g N2O4 g can be written as:Kc = [N2O4] / [NO2]^2Given the concentration of NO2 to be 0.025 mol/L and the concentration of N2O4 to be 0.0105 mol/L at equilibrium, we can now calculate the value of Kc:Kc = 0.0105 / 0.025 ^2Kc = 0.0105 / 0.000625Kc 16.8Therefore, the value of Kc for the given reaction is approximately 16.8.