Reaction profiles effectively illustrate the energy changes that occur during a chemical reaction by depicting the difference in energy between reactants and products.

A reaction profile, also referred to as an energy level diagram, serves as a graphical representation of the energy transformations that take place as reactants convert into products. In this diagram, the vertical axis denotes energy, while the horizontal axis signifies the progress of the reaction.

At the beginning of the reaction, the reactants possess a specific amount of energy, represented by a point on the vertical axis. As the reaction progresses, the energy of the system may either increase or decrease, depending on whether the reaction is endothermic or exothermic. In an endothermic reaction, energy is absorbed from the surroundings, resulting in a rise in the system’s energy, which is illustrated by an upward slope on the reaction profile. Conversely, in an exothermic reaction, energy is released into the surroundings, causing a decrease in the system’s energy, depicted as a downward slope.

The difference in energy between the reactants and the products is known as the enthalpy change, denoted as $\Delta H$. This difference is represented on the reaction profile as the vertical distance between the energy levels of the reactants and the products. If the products have lower energy than the reactants, $\Delta H$ is negative, indicating that the reaction is exothermic. Conversely, if the products possess higher energy than the reactants, $\Delta H$ is positive, indicating that the reaction is endothermic.

Additionally, the reaction profile illustrates the activation energy, denoted as $E_a$, which is the minimum energy required to initiate the reaction. This is represented by the peak of the curve on the diagram. A higher activation energy corresponds to a slower reaction rate, as fewer molecules will have sufficient energy to surpass this energy barrier.

In summary, reaction profiles provide a clear visual representation of the energy changes that occur during a chemical reaction. They convey whether the reaction is endothermic or exothermic, the enthalpy change, and the activation energy required for the reaction to proceed.