AP Chemistry Practice Quiz: Catalysis
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 12 questions to check your progress.
Question 1 of 12
All Questions (12)
A) By increasing the overall enthalpy change of the reaction.
B) By providing an alternative reaction pathway with a lower activation energy.
C) By shifting the equilibrium position to favor the products.
D) By being permanently consumed to form additional products.
Correct Answer: B
The text explicitly states, 'A catalyst increases the rate of reaction by either increasing effective collisions or providing a reaction path with a lower activation energy.' The other options are incorrect descriptions of a catalyst's function. Catalysts do not affect the overall thermodynamics (enthalpy or equilibrium) and are not consumed, as their net concentration remains constant.
A) A catalyst speeds up the existing elementary steps in the original mechanism.
B) A catalyst functions by introducing changes to the reaction mechanism.
C) A catalyst eliminates the rate-determining step of the original mechanism without changing other steps.
D) A catalyst only affects the final step of the reaction mechanism.
Correct Answer: B
The first point in the content is to 'Explain the relationship between the effect of a catalyst on a reaction and changes in the reaction mechanism.' Subsequent points detail how catalysts introduce new intermediates and elementary steps (e.g., covalent bonding, surface binding), which constitutes a change in the mechanism or reaction path.
A) The net concentration decreases as the reaction proceeds.
B) The net concentration increases as it is produced in the reaction.
C) The net concentration remains constant throughout the reaction.
D) The net concentration fluctuates based on the temperature.
Correct Answer: C
The text states, 'In a catalyzed mechanism, the catalyst's net concentration is constant.' This is a defining characteristic of a catalyst; it is regenerated by the end of the reaction cycle.
A) It is a product in the first step and a reactant in the last step.
B) It is produced in an early step and consumed in a later step.
C) It is a reactant in an early step and regenerated as a product in a later step.
D) It is present only in the overall balanced equation but not in the elementary steps.
Correct Answer: C
The content explains, 'It is often consumed in one step (like the rate-determining step) and regenerated in a subsequent step.' This means it first appears as a reactant and is later reformed as a product. Option B describes a reaction intermediate.
A) To permanently sequester the reactants from the solution.
B) To increase the kinetic energy of the reactant molecules.
C) To orient the reactants favorably for a reaction to occur.
D) To change the chemical identity of the reactants into non-reactive species.
Correct Answer: C
The text states that some catalysts work by 'binding to reactants, orienting them favorably or lowering activation energy.' Orienting them favorably increases the chance of an effective collision, thus increasing the reaction rate.
A) requirement of a gaseous reactant.
B) formation of a new reaction intermediate.
C) exclusive use of non-covalent bonds.
D) consumption of the catalyst in the final step.
Correct Answer: B
The text mentions that enzyme-like catalysts form a 'new reaction intermediate,' acid-base catalysis introduces 'new intermediates and elementary steps,' and surface catalysis involves a 'bound intermediate.' Therefore, the formation of new intermediates is a common feature of these catalytic mechanisms.
A) It relies solely on orienting reactants without forming new bonds.
B) It involves the formation of covalent bonds between the catalyst and reactants.
C) It only works for reactions occurring on a solid surface.
D) It decreases the rate of reaction by stabilizing the reactants.
Correct Answer: B
The provided content explicitly states, 'Some catalysts involve covalent bonding with reactants (e.g., acid-base catalysis), introducing new intermediates and elementary steps.' This covalent interaction is a key feature of its mechanism.
A) By dissolving the reactants into a liquid phase.
B) By providing a surface to which a reactant binds, creating new elementary reactions.
C) By absorbing all the heat generated by the reaction.
D) By breaking all bonds in the reactant molecules simultaneously.
Correct Answer: B
The text describes surface catalysis as a process where 'a reactant binds to the surface, creating new elementary reactions involving the bound intermediate.' This binding is the crucial first step in the catalytic cycle.
A) The new mechanism has a more positive Gibbs free energy change.
B) The new mechanism involves fewer elementary steps.
C) The new mechanism provides a pathway with a lower activation energy.
D) The new mechanism forces all collisions to be effective.
Correct Answer: C
The content links the change in mechanism (Point 1) to the increase in rate (Point 2). Point 2 specifies that the rate increases by 'providing a reaction path with a lower activation energy.' The new, catalyzed mechanism is this lower-energy path.
A) A
B) B
C) C
D) AC
Correct Answer: C
The content states that a catalyst is 'consumed in one step... and regenerated in a subsequent step.' In this mechanism, species C is consumed as a reactant in Step 1 and regenerated as a product in Step 2. Species AC is an intermediate, as it is produced in Step 1 and then consumed in Step 2.
A) A catalyst is consumed then regenerated, while an intermediate is produced then consumed.
B) A catalyst is produced then consumed, while an intermediate is consumed then regenerated.
C) A catalyst appears in the overall reaction equation, while an intermediate does not.
D) A catalyst is always a solid, while an intermediate is always in the same phase as the reactants.
Correct Answer: A
The text says a catalyst is 'consumed in one step... and regenerated in a subsequent step.' A reaction intermediate, by definition, is a species that is formed in one elementary step and consumed in a subsequent one. This opposing pattern of consumption and production is their defining difference within a mechanism.
A) By increasing the temperature of the reaction vessel.
B) By binding to reactants and orienting them favorably.
C) By increasing the concentration of the reactants.
D) By changing the phase of the reactants from liquid to gas.
Correct Answer: B
The text provides two ways a catalyst increases the rate: 'increasing effective collisions or providing a reaction path with a lower activation energy.' It then gives a specific example of how effective collisions can be increased: 'Some catalysts work by binding to reactants, orienting them favorably.' Increasing temperature or reactant concentration also increases collisions, but these are changes to reaction conditions, not actions of the catalyst itself.