Determine the following equilibrium:
PCl5 (g) ⇔ PCl3 (g) +Cl2 (g)
At 200°C the 5.0 moles of PCl5 are placed in a 10.0 L flask and allowed to come to equilibrium. Analysis shows that the 1.0 mole of Cl2 is present in the equilibrium mixture. Determine the numbers of moles of PCl5 are present at the equilibrium.