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Question
Does the following reaction represent a thermochemical equation?
\[\ce{CH_{4(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(g)}}\], ∆fH° = –900 kJ mol–1
Solution
No, the given reaction does not represent a thermochemical equation. The given standard enthalpy of reaction (∆rH°) indicates the enthalpy change accompanying the reaction when the reactants and products involved are in their standard states. The standard state of water is H2O(l) and not H2O(g).
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