Phosgene, COCl2, is the chemical warfare gas commonly called mustard gas. It decomposes as written below. At 900 C, the Kc= 0.83. Assume 0.400 mol of COCl2 are admitted into a 2.00 L container at 900C. What will be the equilibrium concentrations of CO, Cl2 and COCl2? USE THE QUADRATIC FORMULA. COCl2 <---> CO + Cl2