Final answer:
A catalyst affects the activation energy of a reaction by providing an alternate reaction pathway with a lower activation energy.
Step-by-step explanation:
A catalyst affects the activation energy of a reaction by providing an alternate reaction pathway with a lower activation energy. This means that the catalyst lowers the energy barrier that reactant molecules need to overcome in order to form the products.
For example, if we compare the potential energy diagrams of a reaction with and without a catalyst, we can see that the catalyst lowers the activation energy of the reaction, as shown in the figure. The catalyst does not affect the energy of the reactants or products, it only provides a lower energy pathway for the reaction to occur.
Therefore, we can conclude that a catalyst lowers the activation energy of a reaction, allowing it to proceed at a faster rate.