AP Chemistry Practice Quiz: Multistep Reaction Energy Profile
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 7 questions to check your progress.
Question 1 of 7
All Questions (7)
A) The activation energy of the first step
B) The energy of the intermediate
C) The overall energy change of the reaction
D) The activation energy of the rate-determining step
Correct Answer: C
The overall energy change (often denoted as ΔH or ΔE) for a reaction is the net difference between the potential energy of the products and the potential energy of the reactants, which is represented on the energy profile.
A) One
B) Two
C) Three
D) It depends on whether the reaction is endothermic or exothermic
Correct Answer: B
Each elementary step in a reaction mechanism has its own transition state and activation energy. Therefore, a two-step mechanism will have two transition states, represented as two peaks on the energy profile.
A) lowest activation energy.
B) highest activation energy.
C) most exothermic energy change.
D) final formation of products.
Correct Answer: B
The rate-determining step is the slowest step in the mechanism. On an energy profile, the slowest step is the one with the largest energy barrier to overcome, which corresponds to the highest activation energy.
A) Only the overall energy change of the reaction
B) Only the chemical formulas of the reactants and products
C) The temperature and pressure at which the reaction occurs
D) The energetics (activation energy and energy change) of each elementary step
Correct Answer: D
As stated in the provided content, knowledge of the energetics of each elementary step in a mechanism is required to construct the complete energy profile, which includes all transition states and intermediates.
A) The final product
B) A reaction intermediate
C) The overall activation energy
D) The initial reactant
Correct Answer: B
In a multistep reaction, the product of one elementary step becomes the reactant for the next. These species, which are formed and then consumed during the reaction, are called intermediates and are represented by the energy minima between the peaks on an energy profile.
A) A low first peak, a high second peak, and products at a lower energy than reactants.
B) A high first peak, a low second peak, and an intermediate at a higher energy level than the reactants.
C) Two peaks of equal height, with products and reactants at the same energy level.
D) A high first peak, a low second peak, and an intermediate at a lower energy level than the reactants.
Correct Answer: B
A large activation energy for the first step means the first peak is high. A highly endothermic first step means the intermediate (the valley after the first peak) is at a significantly higher energy level than the initial reactants. An exothermic second step with a small activation energy means the second peak is relatively low (compared to the intermediate's energy) and the final products are at a lower energy than the intermediate.
A) The energy difference between the highest energy transition state and the initial reactants.
B) The energy difference between the final products and the initial reactants.
C) The energy difference between the second transition state and the reaction intermediate.
D) The energy difference between the second transition state and the final products.
Correct Answer: C
The activation energy for any elementary step is the energy difference between the transition state for that step and the reactants for that step. For the second step, the 'reactants' are the intermediates formed in the first step.