Final answer:
To find the moles of O₂ in equilibrium with 0.5 moles of HCl, Cl₂, and H₂O, the reaction stoichiometry and the equilibrium constant are considered. An ICE table would help in this situation, but without knowing the volume, an exact molarity cannot be calculated.
Step-by-step explanation:
To determine the number of moles of O₂ that can coexist with 0.5 moles each of HCl, Cl₂, and H₂O in a chemical equilibrium represented by the equation 4HCl + O₂ ⇌ 2Cl₂ + 2H₂O, we must consider the stoichiometry of the reaction and the equilibrium constant (Kc) given as 720. If we assume that the system has reached equilibrium, the relative quantities of reactants and products will depend on the Kc value. We can set up an ICE table (Initial, Change, Equilibrium) to help us find the equilibrium concentrations. However, without the total volume of the container, we cannot convert moles to molarity to use the Kc value directly. Assuming the volumes are the same, we can use the mole ratio provided by the balanced chemical equation to find out how much O₂ would have reacted to reach equilibrium with the given amounts of other substances.