Which diagram shows energy as a function of reaction progress and illustrates the activation energy as the gap between reactants and the transition state?

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

Answer: (C)

Energy profile as a reaction proceeds is depicted by a reaction coordinate diagram, where energy is plotted against reaction progress. The highest point along the curve represents the transition state, the activated complex. The activation energy is the vertical gap between the energy of the reactants and that peak. This diagram shows whether the reaction is exothermic or endothermic by the relative heights of reactants and products. The other terms refer to different ideas: activation energy is the barrier itself, not a diagram type; rate law describes how rate depends on concentrations; and Arrhenius relates temperature to rate constants, often shown as a different kind of plot rather than energy versus progress.