An energy profile diagram for an endothermic reaction shows
Correct answer: A. products at a higher energy level than reactants, with an activation barrier in between
- A. products at a higher energy level than reactants, with an activation barrier in between
- B. products at a lower energy level than reactants
- C. no activation energy
- D. reactants and products at the same level
Explanation
In an endothermic reaction energy is absorbed overall, so the products lie above the reactants and the enthalpy change is positive, but the curve must still rise to a peak because the activation barrier has to be crossed. The barrier for the reverse, exothermic direction is correspondingly smaller. Reading the enthalpy change as the difference between the two flat levels, not as the height of the peak, is the key skill.
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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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