Two of the propagation steps in the Cl∙/O3 system consume ozone and oxygen atoms (which are necessary for the production of ozone), respectively (Section 3-9).
CI + O3 → CIO + O2
CIO + O → CI + O2
Calculate ∆H° for each of these propagation steps. Use the following data: DH° for CIO = 64 kcal mol-1; DH° for O2 = 120 kcal mol-1; DH° for an O-O2 bond in O3 = 26 kcal mol-1. Write the overall equation described by the combination of these steps and calculate its ∆H°. Comment on the thermodynamic favorability of the process.