In an energy diagram for a chemical reaction, which part of the graph represents the activation energy?

• A. The energy at the starting point of the reactants
• B. The energy at the ending point of the products
• C. The energy difference between the reactants and the peak of the curve
• D. The energy difference between the reactants and the products

Answer: (C)

Verified step by step guidance

1. Understand that an energy diagram for a chemical reaction plots the potential energy of the system against the reaction progress.
2. Identify the energy level of the reactants at the starting point of the graph and the energy level of the products at the ending point.
3. Locate the highest point on the curve between reactants and products, which represents the transition state or activated complex.
4. Recognize that the activation energy is the energy difference between the reactants and this peak (transition state) on the graph.
5. Therefore, the activation energy corresponds to the energy barrier that must be overcome for the reaction to proceed, which is the difference between the reactants' energy and the peak of the curve.