Which of the following correctly labels the components of an energy diagram for a spontaneous reaction?

• A. Reactants have lower energy than products; the difference in energy is negative (ΔG < 0); activation energy is shown as a peak after the products.
• B. Reactants and products have the same energy; there is no activation energy barrier.
• C. Products have higher energy than reactants; the difference in energy is positive (ΔG > 0); activation energy is shown as a trough below reactants.
• D. Reactants have higher energy than products; the difference in energy is negative (ΔG < 0); activation energy is shown as a peak between reactants and products.

Answer: (D)

Verified step by step guidance

1. Understand that in an energy diagram for a chemical reaction, the vertical axis represents the potential energy of the system, while the horizontal axis represents the progress of the reaction from reactants to products.
2. Recall that for a spontaneous reaction, the Gibbs free energy change (\( \Delta G \)) is negative, meaning the products have lower energy than the reactants.
3. Identify that the difference in energy between reactants and products is given by \( \Delta G = G_{products} - G_{reactants} \), and for spontaneity, this value must be less than zero (\( \Delta G < 0 \)).
4. Recognize that the activation energy is the energy barrier that must be overcome for the reaction to proceed, and it appears as a peak on the energy diagram between the reactants and products.
5. Conclude that the correct energy diagram for a spontaneous reaction shows reactants at a higher energy level than products, a negative \( \Delta G \), and an activation energy peak between them.