Reaction in which heat evolves is called ____________________?
Correct answer: D. exothermic
- A. endothermic
- B. spontaneous
- C. non-spontaneous
- D. exothermic
Explanation
A reaction that evolves or releases heat to its surroundings has a negative enthalpy change and is called exothermic. Students may choose spontaneous because some exothermic reactions occur readily, but heat release does not by itself establish spontaneity.
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About Exothermic and Endothermic Reactions
Exothermic reactions release heat to the surroundings and have negative enthalpy change, while endothermic reactions absorb heat and have positive enthalpy change. The topic uses energy profiles to identify reactants, products and activation energy, and includes bond energy, enthalpy diagrams, calorimetry and Hess's law for calculating overall heat changes.
Practise Thermochemistry and Energetics of Chemical Reactions
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