'∆H' Will be given a negative sign in:
Correct answer: A. Exothermic reactions
- A. Exothermic reactions
- B. Decomposition reactions
- C. Dissociation reactions
- D. Endothermic reactions
Explanation
In exothermic reactions, the system releases heat to the surroundings, causing the enthalpy change (∆H) to be negative. This is because the products of the reaction have lower energy than the reactants. Decomposition reactions can be either exothermic or endothermic, so ∆H is not always negative. Dissociation reactions generally require energy input, making them endothermic with a positive ∆H. Endothermic reactions absorb energy, resulting in a positive ∆H, which is the opposite of exothermic reactions.
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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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