Which of the following energy profile diagrams best illustrates an endothermic reaction with high activation energy?

• A. A diagram where the reactants and products are at the same energy level, with a moderate activation energy peak.
• B. A diagram where the reactants start at a lower energy, the activation energy peak is very high, and the products end at a higher energy than the reactants.
• C. A diagram where the reactants start at a lower energy, the activation energy peak is low, and the products end at a higher energy than the reactants.
• D. A diagram where the reactants start at a higher energy, the activation energy peak is low, and the products end at a lower energy than the reactants.

Answer: (B)

Verified step by step guidance

1. Understand that an endothermic reaction absorbs energy, so the products have higher energy than the reactants. This means the energy level of the products should be above that of the reactants on the energy profile diagram.
2. Recognize that activation energy (Ea) is the energy barrier that must be overcome for the reaction to proceed. A high activation energy means the peak of the energy curve (the transition state) is significantly higher than the reactants' energy level.
3. Look for a diagram where the reactants start at a lower energy level, the activation energy peak is very high (indicating a large energy barrier), and the products end at a higher energy level than the reactants (indicating an endothermic reaction).
4. Exclude diagrams where the reactants and products are at the same energy level, as this would represent a thermoneutral reaction, not endothermic.
5. Exclude diagrams with low activation energy peaks or where products are at lower energy than reactants, as these represent either exothermic reactions or reactions with low energy barriers.