In the iodination of ethane shown below, tetraiodomethane (CI₄) is used as the source of iodine in the presence of a free-radical initiator such as hydrogen peroxide (H₂O₂).
Propose a mechanism for the reaction, and determine the value of ∆H for each of the steps in your mechanism using the appropriate bond-dissociation energies.

H₃C−CH₃ + CI₄ → H₃C−CH₂I + HCI₃