All of the following standard enthalpy change (∆H°) have only positive value EXCEPT:
Correct answer: B. ∆H°sol
- A. ∆Hv
- B. ∆H°sol
- C. ∆H°BDE
- D. ∆Hi
Explanation
Option B, ∆H°sol, refers to the standard enthalpy change of solution, which is the enthalpy change when one mole of a substance dissolves in a large excess of solvent to form a solution of infinite dilution under standard conditions.The reason why option B is correct, and all other options are incorrect, is because ∆H°sol can be either positive or negative. It depends on whether the dissolution process is exothermic (releases heat) or endothermic (absorbs heat).
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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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