An equilibrium mixture of SO2, SO3 and O2 gases is maintained in a 11.5 L flask at a temperature at which Kc = 55.2 for the reaction shown below. If the number of moles of SO3 in the flask at equilibrium is twice the number of moles of SO2, how much O2 is present in the flask at equilibrium? Show all work.
2 SO2 (g) + O2 (g) ? 2 SO3 (g)