All of the following reactions are exothermic EXCEPT:
Correct answer: C. C
- A. A
- B. B
- C. C
- D. D
Explanation
N₂(g) + O₂(g) → 2NO(g) is endothermic, meaning it absorbs heat from its surroundings (it has a positive ΔH value, around +180.6 kJ/mol). This is an exception among the other options, which are all combustion or formation reactions that are typically exothermic.
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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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