The given diagram shows the enthalpy changes during a chemical reaction. What type of reaction is this?
Correct answer: B. An exothermic reaction
- A. An endothermic reaction
- B. An exothermic reaction
- C. An isothermic process
- D. A non-spontaneous process
Explanation
This diagram shows a reaction in which the reactants are at a greater energy level than the products, indicating that energy is released during the reaction, i.e. change in enthalpy or (H2-H1) would be negative, indicating that it is an exothermic reaction so, option B is correct.Option A describes an endothermic reaction which would have a diagram depicting products, at a higher energy level than the reactants.Option C indicates a process in which the heat energy of the system does not change, but the diagram itself shows a change in enthalpy.Option D cannot be determined from a mere energy diagram as shown.
This question appeared on the UHS MDCAT 2019 paper, which you can sit online with every answer explained.
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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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