AP Chemistry Quiz: Reaction Energy Profile
2 questions · exam conditions
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Reaction Energy ProfileQuestion 1 of 2

A chemist proposes two different single-step pathways for converting the same reactants to the same products. The reaction energy profile diagram shows two curves: Pathway 1 has a lower peak than Pathway 2, while both start at the same reactant energy level and end at the same product energy level. Based on the diagram, which statement correctly compares the initial reaction rates at the same temperature (with all other conditions identical)?

Pathway 2 is faster because its products are at the same energy as Pathway 1, so the rate must be the same.
Pathway 1 is faster because it has the smaller activation-energy barrier (lower peak above the reactants).
Pathway 2 is faster because its activation energy is larger, which increases the number of effective collisions.
Pathway 1 is faster because its products are lower in energy than the reactants, so it is more spontaneous.
Pathway 2 is faster because its curve is steeper on the way to the peak, indicating a faster rate.
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AP Chemistry Quiz

AP Chemistry Quiz: Reaction Energy Profile

Practice Reaction Energy Profile in AP Chemistry with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Reaction Energy Profile, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Chemistry.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A chemist proposes two different single-step pathways for converting the same reactants to the same products. The reaction energy profile diagram shows two curves: Pathway 1 has a lower peak than Pathway 2, while both start at the same reactant energy level and end at the same product energy level. Based on the diagram, which statement correctly compares the initial reaction rates at the same temperature (with all other conditions identical)?

  1. Pathway 2 is faster because its products are at the same energy as Pathway 1, so the rate must be the same.
  2. Pathway 1 is faster because it has the smaller activation-energy barrier (lower peak above the reactants). (correct answer)
  3. Pathway 2 is faster because its activation energy is larger, which increases the number of effective collisions.
  4. Pathway 1 is faster because its products are lower in energy than the reactants, so it is more spontaneous.
  5. Pathway 2 is faster because its curve is steeper on the way to the peak, indicating a faster rate.
Explanation: This question tests understanding of reaction energy profiles. The activation energy is the vertical distance from the reactants to the peak of the energy curve, which represents the minimum energy barrier that must be overcome for the reaction to proceed. Since Pathway 1 has a lower peak than Pathway 2 (both starting from the same reactant energy), Pathway 1 has the smaller activation energy. According to the Arrhenius equation, reactions with lower activation energies have faster rates at the same temperature because more molecules possess sufficient energy to overcome the barrier. Choice D incorrectly confuses thermodynamic favorability (product stability) with kinetic rate—a reaction can be thermodynamically favorable but still slow if the activation barrier is high. To determine reaction rate from an energy profile, always measure the height of the barrier from reactants to peak, not the final energy of products.

Question 2

The reaction energy profile diagram shows a single-step reaction with one peak. A catalyst is introduced that provides an alternative single-step pathway (still one peak) between the same reactants and products. Which change must be shown on the diagram for the catalyzed pathway compared with the uncatalyzed pathway?

  1. The catalyzed pathway must have a higher peak because catalysts increase collision frequency.
  2. The catalyzed pathway must have reactants at a lower energy level than before.
  3. The catalyzed pathway must have products at a lower energy level than before.
  4. The catalyzed pathway must have the same peak height but a steeper curve.
  5. The catalyzed pathway must have a lower peak (smaller activation-energy barrier) while starting and ending at the same energy levels. (correct answer)
Explanation: This question tests understanding of how catalysts affect reaction energy profiles. A catalyst provides an alternative reaction pathway with a lower activation energy, which appears on the diagram as a lower peak between the same reactants and products. The catalyst does not change the energies of reactants or products (thermodynamics remains unchanged), only the height of the energy barrier that must be overcome. This lower activation energy allows more molecules to react at a given temperature, increasing the reaction rate. Choice A incorrectly suggests catalysts raise the peak—catalysts never increase activation energy, and they work by lowering the barrier, not by increasing collision frequency. When identifying catalyzed pathways on energy diagrams, look for the same starting and ending points but with a lower peak in between.