The equilibrium constant for the gas phase reaction 2so2 (g) + o2 (g) 2so3 (g) is keq = 2.80 ⋅ 102 at 999 k. at equilibrium, the equilibrium constant for the gas phase reaction 2so2 (g) + o2 (g) 2so3 (g) is keq = 2.80 102 at 999 k. at equilibrium, products predominate reactants predominate roughly equal amounts of products and reactants are present only products are present only reactants are present