Phosgene, COCl₂(g), is a toxic gas used as an agent of warfare in World War I. (b) Using the table of bond dissociation energies (Table 9.3) and the value ΔH°f = 716.7 kJ/mol for C(g), estimate ΔH°_f for COCl₂(g) at 25 °C. Compare your answer to the actual ΔH°_f given in Appendix B, and explain why your calculation is only an estimate.