A plot of energy versus reaction progress is called what?

• A. Catalyst
• B. Activation energy
• C. Rate Law
• D. Reaction coordinate diagram

Answer: (D)

A reaction coordinate diagram shows the energy of a system as the reaction progresses from reactants to products along the reaction pathway. The peak corresponds to the transition state, and the vertical distance from reactants to that peak is the activation energy—the energy barrier that must be overcome. The overall energy difference between reactants and products is the reaction’s enthalpy change. Catalysts lower the barrier by providing an alternate, lower-activation-energy pathway, altering the diagram without changing the final energy of the products. A rate law describes how the rate depends on concentrations, not the energy profile. So the plot of energy versus reaction progress is a reaction coordinate diagram.