Final answer:
The reaction diagram with two transition states and a lower activation energy corresponds to the reaction with an added catalyst, as catalysts provide a pathway with a lower activation energy for the reaction.
Step-by-step explanation:
The question is asking to compare two reaction diagrams for a chemical process to estimate the activation energy for each and identify which one involves a catalyst. Catalysts provide an alternative reaction mechanism with a lower activation energy to accelerate reactions. The graph with two transition states and a lower initial activation energy compared to the graph with one transition state is most likely the one with the catalyst added.
Often, the uncatalyzed reaction proceeds via a one-step mechanism with a higher activation energy, which can be seen as a single peak in the energy diagram. In contrast, the catalyzed reaction typically follows a multi-step mechanism that features a series of peaks reflecting lower activation energies for each step, indicative of the presence of a catalyst. This is because the catalyst offers a new pathway with lower energy requirements for the reaction to proceed.