Multiple Choice
In an energy diagram for a chemical reaction, which part of the graph represents the activation energy?
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15. Chemical Kinetics
Energy Diagrams
Multiple Choice
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.
Verified step by step guidance1
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.
Recall that for a spontaneous reaction, the Gibbs free energy change (\( \Delta G \)) is negative, meaning the products have lower energy than the reactants.
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 (\( \Delta G < 0 \)).
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.
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.
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