Question

Phosgene, Cl2CO, is a highly toxic gas that was used as a weapon in World War I. Using the bond dissociation enthalpies in the table, estimate the enthalpy change for the reaction of carbon monoxide and chlorine to produce phosgene.

CO(g) + Cl2(g) Cl2CO(g)

Answer 1

I don't have those bond energies memorized but here is how you do it.
CO + Cl2 ==> COCl2
Delta Hrxn = BE reactants - BE product
delta Hrxn = [BE CO] + [BE Cl-Cl] - [BE CO] - 2*[BE C-Cl]