If a catalyst for the first elementary step is added to the system, what do you expect to happen to the plot of the potential energy diagram?
When a catalyst is added to a system, it typically speeds up the reaction by providing an alternative pathway with a lower activation energy. This allows the reaction to proceed at a faster rate, but it does not affect the overall energy change or the equilibrium position of the reaction.
In terms of the potential energy diagram, the addition of a catalyst leads to a change in the reaction pathway. The catalyst provides a new route for the reaction to occur, typically involving a different intermediate or transition state. As a result, the energy profile of the reaction will change.
Specifically, the addition of a catalyst will result in a decrease in the activation energy for the reaction. The peak of the energy diagram corresponding to the rate-determining step (the step with the highest activation energy) will be lower in the presence of a catalyst. This change in the activation energy barrier allows the reactant molecules to more easily overcome the energy barrier and proceed to the product side. Therefore, the plot of the potential energy diagram will exhibit a lower energy barrier for the catalyzed reaction compared to the uncatalyzed reaction.
In summary, the addition of a catalyst to a reaction system will lower the activation energy barrier and result in a lower energy peak on the potential energy diagram. This reflects the increased reaction rate facilitated by the catalyst.