∆Hr of compound is:
Correct answer: D. sometimes positive and sometimes negative
- A. Zero in standard state
- B. Always negative
- C. Always positive
- D. sometimes positive and sometimes negative
Explanation
In an exothermic reaction, heat energy is released from the compound, therefore ∆Hr is negative. However, in an endothermic reaction, heat energy is absorbed by the compound, therefore ∆Hr is positive.
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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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