The chemical hand warmers described in Section 6.1 produce heat when they are removed from their airtight plastic wrappers. Recall that they utilize the oxidation of iron to form iron oxide according to the reaction: 4Fe(s) + 3O2(g) ----> 2Fe2O3(s). Calculate H rxn for this reaction and compute how much heat is produced from a hand warmer containing 15.0 grams of iron powder.