Question 3 • Chemistry
Use ΔH_rxn = ΣΔH_f(products) − ΣΔH_f(reactants). CO₂(g) has ΔH_f = −393.5 kJ/mol, while C(s) and O₂(g) are elements in their standard states, so each has ΔH_f = 0. Thus ΔH_rxn = −393.5 − (0 + 0) = −393.5 kJ, the value in choice A.
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