Draw a reaction coordinate diagram for an exothermic...

Draw a reaction coordinate diagram for an exothermic reaction that occurs in a single step. Mark the activation energy, and identify the net energy change for the reaction on this diagram. Draw a second diagram that represents the same reaction in the presence of a catalyst. Identify the activation energy of this reaction and the energy change. Is the activation energy in the two drawings different? Does the energy evolved in the two reactions differ?

Key Concepts

Activation Energy

Activation energy is the minimum amount of energy required for reactants to reach the transition state and form products. It represents the energy barrier that must be overcome for the reaction to proceed. In the context of the diagram, the activation energy is depicted as the height difference between the reactants and the peak of the energy curve at the transition state.

Catalyst

A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. Importantly, while a catalyst lowers the energy barrier, it does not alter the overall energy change (thermodynamics) of the reaction. On a reaction coordinate diagram, the presence of a catalyst is shown by a lower peak in the energy profile compared to the uncatalyzed reaction.

Reaction Coordinate Diagram

A reaction coordinate diagram is a graphical representation that plots the potential energy of the system along the reaction pathway, starting from reactants to products. It illustrates the energy changes that occur during a chemical reaction, including the formation of the transition state and the release or absorption of energy. This diagram is essential for visualizing energy barriers and for understanding the kinetics and thermodynamics of the reaction.

Exothermic Reaction

An exothermic reaction is one in which energy is released to the surroundings, typically in the form of heat. On a reaction coordinate diagram, the products are shown to be at a lower energy level than the reactants, indicating that the overall energy change for the reaction is negative. This release of energy can contribute to driving the reaction forward.

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