The thermite reaction, in which powdered aluminum reacts with iron oxide, is highly exothermic: 2al(s)  +  f e2o3 (s)→a l2o 3 (s)  +  2fe(s) use standard enthalpies of formation to find δh ∘ rxn for the thermite reaction.

For this problem, we use the Hess' Law.

ΔHrxn = ∑(ν*Hf of products) - ∑(ν*Hf of reactants)

The ν represents the corresponding stoichiometric coefficients of the substances, while Hf is the heat of formation. For pure elements, Hf = 0.

Hf of Al₂O₃ = −1676.4 kJ/mol
Hf of Fe₂O₃ = -826.0 kJ/mol

Thus,

ΔHrxn = 1*−1676.4 kJ/mol + 1*-826.0 kJ/mol
ΔHrxn = -2502.4 kJ/mol

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