Bond breaking and bond formation are respectively
Correct answer: D. endothermic and exothermic
- A. both exothermic
- B. both endothermic
- C. exothermic and endothermic
- D. endothermic and exothermic
Explanation
Energy must be supplied to pull bonded atoms apart, so breaking is endothermic, while forming a bond releases energy and is exothermic. Whether the overall reaction is exothermic depends on which total is larger, so a reaction releasing more energy in making new bonds than it spends breaking old ones is exothermic. This is the reasoning behind calculating enthalpy change from bond energies.
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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.
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