AP Chemistry Practice Quiz: 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 11 questions to check your progress.
Question 1 of 11
All Questions (11)
A) The energy difference between the reactants and the products.
B) The energy difference between the reactants and the transition state.
C) The absolute energy of the transition state.
D) The energy difference between the transition state and the products.
Correct Answer: B
The provided content explicitly states, 'The activation energy is the energy difference between reactants and the transition state.'
A) The total time elapsed during the reaction.
B) The change in temperature of the system.
C) The progress of the reaction as reactants are rearranged into products.
D) The concentration of the reactants over time.
Correct Answer: C
The text defines the reaction coordinate as plotting 'the energy of the complex set of motions involved in rearranging reactants to form products,' which represents the progress of the reaction.
A) All reactant bonds have been broken, and no product bonds have formed yet.
B) The final products have just been formed and are at their highest energy.
C) Reactant bonds are in the process of breaking while new product bonds are simultaneously forming.
D) The reactants are colliding, but no bond rearrangement has begun.
Correct Answer: C
The transition state is the highest energy point where reactants are being rearranged into products. This involves the 'complex set of motions' where, as the text states, 'the breaking of some bonds and the forming of new ones' is in progress.
A) It lowers the energy of the transition state, making it easier to reach.
B) It decreases the overall energy change of the reaction.
C) It increases the proportion of molecular collisions that have sufficient energy to reach the transition state.
D) It changes the reaction coordinate pathway to one with a lower activation energy.
Correct Answer: C
The content states that 'temperature affects the proportion of collisions with enough energy to reach the transition state.' An increase in temperature increases this proportion, thus increasing the reaction rate.
A) The reactants and the transition state.
B) The transition state and the products.
C) The starting point of the reaction coordinate and the highest energy point.
D) The reactants and the products.
Correct Answer: D
The content requires the representation of the 'overall energy change'. This is the net change from the beginning (reactants) to the end (products) of the reaction.
A) The reaction will have a large, negative overall energy change.
B) The reaction will proceed very quickly because the transition state is highly unstable.
C) A smaller proportion of reactant collisions will have sufficient energy to form the transition state.
D) The energy of the products must be much higher than the energy of the reactants.
Correct Answer: C
A high activation energy means a large amount of energy is required to get from reactants to the transition state. According to the text, this means a smaller 'proportion of collisions with enough energy to reach the transition state' will exist, leading to a slower reaction rate.
A) The change in reactant concentration over time.
B) The energy changes associated with bond breaking and bond formation.
C) The effect of a catalyst on the reaction mechanism.
D) The equilibrium constant for the overall reaction.
Correct Answer: B
The profile plots the energy changes as reactants are converted to products. The text explicitly links elementary reactions to the 'breaking of some bonds and the forming of new ones,' which is the process whose energy is being tracked.
A) The overall energy change of the reaction.
B) The stability of the final products.
C) The proportion of collisions possessing sufficient energy to reach the transition state.
D) The specific sequence of bond-breaking events.
Correct Answer: C
The text directly links the Arrhenius equation to the concept that 'temperature affects the proportion of collisions with enough energy to reach the transition state.'
A) The activation energy is equal to the overall energy change.
B) The activation energy is a positive value that is greater than the overall energy change.
C) The activation energy is negative.
D) The reaction is exothermic, and the activation energy is less than the overall energy change.
Correct Answer: B
If products are higher in energy than reactants, the overall energy change is positive (endothermic). The activation energy is the energy from the reactants to the peak of the profile (the transition state), which is always the highest point. Therefore, the activation energy must be a positive value and larger than the energy difference between the final products and the initial reactants.
A) A greater fraction of molecules possesses the minimum energy required for a reaction to occur.
B) The activation energy of the reaction is lowered.
C) The proportion of collisions with energy equal to or greater than the activation energy increases.
D) More molecules have enough energy to reach the transition state.
Correct Answer: B
The provided text states that temperature affects the 'proportion of collisions with enough energy'. It does not state that temperature changes the energy profile itself or lowers the activation energy. The activation energy is an intrinsic property of the reaction pathway.
A) The linear distance between reactant and product molecules in the reaction vessel.
B) The progression of continuous changes in bond lengths and angles as the system moves from reactants to products.
C) The amount of heat released or absorbed by the reaction at any given moment.
D) The average kinetic energy of the molecules involved in a successful collision.
Correct Answer: B
The text describes the reaction coordinate in terms of the 'complex set of motions involved in rearranging reactants to form products.' This physical rearrangement involves the stretching and breaking of old bonds and the formation of new ones, which corresponds directly to a progression of changes in bond lengths and angles.