What is an energy diagram?

• A. Energy diagram
• B. Reaction intermediate
• C. Integrated rate law
• D. Overall order

Answer: (A)

An energy diagram is a plot of the system’s potential energy as the reaction progresses along the reaction coordinate. It shows reactants and products as energy levels, with a peak that represents the transition state. The height of that peak is the activation energy, which controls how fast the reaction can proceed. The difference in energy between reactants and products shows the overall enthalpy change of the reaction. Catalysts appear as a lower peak, illustrating how they speed up the process by lowering the activation energy without changing the overall energy change. This visualization is different from a reaction intermediate, which would appear as a distinct energy minimum along the path; from an integrated rate law, which describes concentration versus time; and from the overall order, which is a kinetic property derived from the rate law.