To determine the equilibrium constant for the reaction A2(g)+B2(g)=2AB(g), a one-liter flask is filled with 0.25 moles of A2 and 0.50 moles of B2. At equilibrium, 0.125 moles of A2 were found to be present. What is the equilibrium constant for the reaction? 0.33 5.33 1.33 2.67