Which of the following reaction is the definition of ∆H"?
Correct answer: A. C(diamond) + O2(g) → CO2(g)
- A. C(diamond) + O2(g) → CO2(g)
- B. H2(g)+F2(g)2HF(g)
- C. N2(g) + 3H2(g)2NH3(g)
- D. CO(g) + O2(g) → CO2(g)
Explanation
The definition of ∆H is the heat of formation of a compound. It is the amount of heat that is released or absorbed when 1 mole of a compound is formed from its constituent elements in their standard states.The reaction that defines ∆H is the formation reaction of the compound. For example, the formation reaction of carbon dioxide is:C(s) + O2(g) → CO2(g).This reaction is the definition of ∆H because it is the reaction that releases the heat of formation of carbon dioxide.
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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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