AP Chemistry Practice Quiz: Introduction to Reaction Mechanisms
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 final balanced equation for a chemical reaction.
B) A series of sequential elementary reactions that describe how a reaction occurs.
C) A substance that increases the rate of a reaction without being consumed.
D) A species that is produced in one step and consumed in a later step.
Correct Answer: B
According to the provided content, a reaction mechanism is defined as a series of sequential elementary reactions (steps) that show the pathway from reactants to products.
A) It appears as a reactant in the overall balanced equation.
B) It is produced in an elementary step and consumed in a subsequent step.
C) It is present at the beginning of the reaction and is regenerated at the end.
D) It is the final substance formed in the overall reaction.
Correct Answer: B
The provided content states that a reaction intermediate is produced by one elementary step and consumed by a subsequent step, meaning it exists only during the reaction.
A) A + B → C
B) C + D → E
C)
D) A + B + D → E
Correct Answer: D
The elementary steps of a mechanism must sum to the overall balanced equation. The species 'C' is an intermediate because it is produced in Step 1 and consumed in Step 2. It cancels out, leaving the overall equation: A + B + D → E.
A) O₃
B) O₂
C) O
D) There is no intermediate in this mechanism.
Correct Answer: C
A reaction intermediate is formed in one step and consumed in a later step. The atomic oxygen (O) is produced in Step 1 and consumed in Step 2, so it is the reaction intermediate.
A) To identify the rate-determining step.
B) To determine the activation energy.
C) To ensure the mechanism is consistent with the overall balanced equation.
D) To identify all the catalysts involved in the reaction.
Correct Answer: C
The provided content states that the elementary steps of a mechanism must sum to the overall balanced equation of the chemical reaction. This is a key criterion for a valid mechanism.
A) The overall reaction is found to be first order.
B) The final products are confirmed to be X₂ and Y₂.
C) The species X₂Y is experimentally detected, even at low concentrations, while the reaction is in progress.
D) The reactants X₂ and Y are shown to be completely consumed at the end of the reaction.
Correct Answer: C
The provided content explicitly states that experimentally detecting a reaction intermediate provides evidence for one reaction mechanism over an alternative.
A) Reactants
B) Products
C) Intermediates
D) Unrelated spectator ions
Correct Answer: D
The content specifies that a reaction mechanism may include reactants, intermediates, products, and catalysts. Unrelated spectator ions are not part of the sequence of elementary steps that constitute the mechanism.
A) NO₂ is an intermediate because it is consumed in Step 2.
B) F is an intermediate because it is produced in Step 1 and consumed in Step 2.
C) F₂ is a product because it is a reactant in Step 1.
D) NO₂F is a catalyst because it is produced in both steps.
Correct Answer: B
The fluorine atom (F) fits the definition of a reaction intermediate: it is produced in the first elementary step and consumed in a subsequent (the second) elementary step. NO₂ and F₂ are reactants, and NO₂F is the product.
A) X + W → Z + P
B) 2X + Y + W → Y + Z + X + P
C) X + Y + W → Z + P
D) W → Z + P
Correct Answer: A
To find the overall reaction, sum the elementary steps and cancel species appearing on both sides. 'Y' is an intermediate and cancels out. One 'X' on the product side cancels one of the two 'X's on the reactant side, leaving X + W → Z + P.
A) Because they are always catalysts that are regenerated.
B) Because they exist only in the transition state.
C) Because they are produced and then consumed during the reaction's elementary steps.
D) Because their concentrations are too small to be significant.
Correct Answer: C
Based on the provided content, an intermediate is produced in one step and consumed in a subsequent step. When the steps are summed to get the overall equation, the intermediate appears on both the reactant and product sides and is therefore canceled out.
A) A and C are reactants; B is an intermediate; D and E are products.
B) A is a reactant; B and C are intermediates; D and E are products.
C) A and B are reactants; C is an intermediate; D and E are products.
D) A, B, and C are reactants; D is an intermediate; E is a product.
Correct Answer: A
A and C are consumed and are the initial starting materials, so they are reactants. B is produced in Step 1 and consumed in Step 2, making it a reaction intermediate. D and E are the final species formed, making them products. This aligns with the definitions of the components of a reaction mechanism.