Given the balanced equation:
4Fe(s) + 3O2(g) ==>2Fe2O3(s) + 1640 kJ
Which phrase best describes this reaction?
(1) endothermic with DH = +1640 kJ
(2) endothermic with DH = -1640 kJ
(3) exothermic with DH = +1640 kJ
(4) exothermic with DH = -1640 kJ
The answer is (4) exothermic with ΔH = -1640 kJ. The 1640 kJ energy is at the right side of equation means that it releases energy. The enthalpy change means the energy of production minus the energy of reactants. If it is exothermic, the ΔH < 0.
