An acid-Base Reaction is always a/an __________?
Correct answer: B. Exothermic
- A. Endothermic
- B. Exothermic
- C. Fission
- D. Fusion
Explanation
Neutralization of an acid by a base usually releases heat because H+ ions combine with OH− ions to form stable water molecules, making the enthalpy change negative. Thus ordinary aqueous acid-base neutralization is exothermic. Students may choose endothermic by thinking that bonds must be broken, but bond formation and hydration release more energy than is absorbed in the usual case.
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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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