Which one of the following equations correctly defines the enthalpy changes of formation of carbon monoxide:
Correct answer: A. C(s) + 1/2 O2 -> CO(g)
- A. C(s) + 1/2 O2 -> CO(g)
- B. C(g) + 1/2 O2 -> CO(g)
- C. C(s) + O(g) -> CO(g)
- D. C(g) + CO2 (g) -> 2CO(g)
Explanation
Since we are talking about the enthalpy of formation, we must ensure that the product has only one mole and the reactants are in their elemental forms. The answer is A since carbon naturally exists as a solid whereas Oxygen gas exists as diatomic molecules. Moreover, stoichiometry must also be considered in which equal moles of carbon and oxygen are present on both, the product and the reactant side.
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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