---
title: "AP Chemistry Unit 5 Practice Test"
description: "A timed AP Chemistry Unit 5 (Kinetics) practice test in the AP format, drawn from 3,072 multiple-choice questions and 56 FRQs written for the unit. The standard version takes about 60 minutes."
canonical: "https://fiveable.me/ap-chem/unit-test/5"
type: "unit-test"
subject: "AP Chemistry"
unit: "Unit 5"
---

# AP Chemistry Unit 5 Practice Test

## Overview

A timed AP Chemistry Unit 5 (Kinetics) practice test in the AP format, drawn from 3,072 multiple-choice questions and 56 FRQs written for the unit. The standard version takes about 60 minutes.

## Test Format

- 20 Multiple Choice Questions (30 minutes)
- 1 FRQ – FRQ 1 – Long Answer (15 minutes)
- 1 FRQ – FRQ 4 – Short Answer (15 minutes)

## Unit FRQs by Type

- [FRQ 1 – Long Answer](/ap-chem/frqs/frq-1?unit=5): 4 questions
- [FRQ 2 – Long Answer](/ap-chem/frqs/frq-2?unit=5): 5 questions
- [FRQ 3 – Long Answer](/ap-chem/frqs/frq-3?unit=5): 7 questions
- [FRQ 4 – Short Answer](/ap-chem/frqs/frq-4?unit=5): 15 questions
- [FRQ 5 – Short Answer](/ap-chem/frqs/frq-5?unit=5): 10 questions
- [FRQ 6 – Short Answer](/ap-chem/frqs/frq-6?unit=5): 6 questions
- [FRQ 7 – Short Answer](/ap-chem/frqs/frq-7?unit=5): 9 questions

## Practice Questions

### Question 1

For the gas-phase reaction $$2N_2O_5(g) \rightarrow 4NO_2(g) + O_2(g)$$, the rate of the reaction can be expressed in terms of the disappearance of reactants or the appearance of products. Which of the following correctly describes the relationship between the rate of appearance of $$NO_2$$ and the rate of disappearance of $$N_2O_5$$?

- (A) It is twice the rate of disappearance of $$N_2O_5$$
- (B) It is equal to the rate of disappearance of $$N_2O_5$$
- (C) It is half the rate of disappearance of $$N_2O_5$$
- (D) It is four times the rate of disappearance of $$N_2O_5$$

**Answer: (A)** Connecting stoichiometry to reaction rates requires using the coefficients from the balanced equation. Since 4 moles of $$NO_2$$ form for every 2 moles of $$N_2O_5$$ consumed, the rate of $$NO_2$$ appearance is $$\frac{4}{2}$$ or 2 times the rate of $$N_2O_5$$ disappearance.

### Question 2

The decomposition reaction $$2A(g) \rightarrow B(g)$$ is determined to be second order with respect to reactant $$A$$. If the initial concentration of $$A$$ is tripled while holding temperature constant, which of the following describes the change in the initial reaction rate?

- (A) The rate increases by a factor of 9
- (B) The rate increases by a factor of 3
- (C) The rate increases by a factor of 6
- (D) The rate increases by a factor of 27

**Answer: (A)** Analyzing the power relationship in the rate law $$Rate = k[A]^2$$ reveals the magnitude of the change. Tripling the concentration ($$3[A]$$) results in a rate proportional to $$(3)^2$$, causing the rate to increase by a factor of 9.

### Question 3

For the elementary gas-phase reaction $$A(g) + B(g) \rightarrow C(g)$$, the rate law is $$Rate = k[A][B]$$. If the volume of the reaction container is halved at constant temperature, how does the reaction rate change?

- (A) The rate quadruples because the concentration of each gas doubles
- (B) The rate doubles because the partial pressure of each gas doubles
- (C) The rate remains constant because the rate constant $$k$$ is unchanged
- (D) The rate halves because the volume reduction limits particle motion

**Answer: (A)** Relating volume to concentration requires recognizing that $$C = n/V$$, so halving volume doubles the concentration of both gases. Substituting these doubled concentrations into the rate law ($$Rate = k(2[A])(2[B])$$ results in a fourfold increase ($$2 \times 2 = 4$$).

### Question 4

The combustion of ammonia proceeds according to the balanced equation $$4NH_3(g) + 5O_2(g) \rightarrow 4NO(g) + 6H_2O(g)$$. Which of the following correctly describes the relationship between the rate of consumption of oxygen and the rate of production of water?

- (A) The rate of $$O_2$$ consumption is $$5/6$$ times the rate of $$H_2O$$ production
- (B) The rate of $$O_2$$ consumption is $$6/5$$ times the rate of $$H_2O$$ production
- (C) The rate of $$O_2$$ consumption is $$4/5$$ times the rate of $$H_2O$$ production
- (D) The rate of $$O_2$$ consumption is $$5/4$$ times the rate of $$H_2O$$ production

**Answer: (A)** Using the stoichiometry of the balanced equation, $$5$$ moles of $$O_2$$ are consumed for every $$6$$ moles of $$H_2O$$ produced. Therefore, the rate of $$O_2$$ change is scaled by the ratio of their coefficients ($$5/6$$) relative to the rate of $$H_2O$$ change.

### Question 5

A decomposition reaction of compound $$XY$$ is found to be zero order with respect to $$XY$$. If the initial concentration of $$XY$$ is doubled, which of the following best describes the effect on the initial reaction rate?

- (A) The initial rate remains the same because it is independent of $$[XY]$$
- (B) The initial rate doubles because it is directly proportional to $$[XY]$$
- (C) The initial rate quadruples because it depends on the square of $$[XY]$$
- (D) The initial rate halves because the reaction time increases with $$[XY]$$

**Answer: (A)** Applying the definition of a zero-order rate law ($$Rate = k[XY]^0$$) reveals that the rate depends only on the rate constant $$k$$. Therefore, changing the concentration of the reactant has no mathematical effect on the reaction rate.

### Question 6

For a reaction with the rate law $$Rate = k[X][Y]^2$$, an experiment is performed where the concentration of $$X$$ is doubled and the concentration of $$Y$$ is halved simultaneously. How does the new initial reaction rate compare to the original rate?

- (A) The rate becomes half the original rate
- (B) The rate becomes double the original rate
- (C) The rate remains equal to the original rate
- (D) The rate becomes four times the original rate

**Answer: (A)** Substituting the changes into the rate law reveals the net effect: $$Rate_{new} = k(2[X])(0.5[Y])^2$$. The factors become $$2 \times (0.5)^2 = 2 \times 0.25 = 0.5$$. Thus, the new rate is $$0.5$$ times the original rate.

### Question 7

A solid cube of reactant is cut into eight smaller, identical cubes. Assuming the reaction rate is directly proportional to the surface area of the solid reactant, which of the following describes the change in the initial reaction rate?

- (A) The rate doubles because the total surface area doubles
- (B) The rate quadruples because the total surface area quadruples
- (C) The rate remains constant because the total mass is constant
- (D) The rate increases by a factor of 8 due to particle number

**Answer: (A)** Analyzing the geometry shows that cutting a cube of side $$L$$ into 8 cubes of side $$L/2$$ increases the total surface area from $$6L^2$$ to $$8 \times 6(L/2)^2 = 12L^2$$. Since rate is proportional to surface area, the rate doubles.

### Question 8

A graph of concentration versus time for the decomposition of $$N_2O_5$$ shows a curve. A tangent line drawn at $$t=0$$ passes through the points $$(0 \text{ s}, 0.50 \text{ M})$$ and $$(50 \text{ s}, 0.30 \text{ M})$$. Based on this line, what is the initial rate of disappearance of $$N_2O_5$$?

- (A) $$0.0040 \text{ M/s}$$
- (B) $$0.0060 \text{ M/s}$$
- (C) $$0.0100 \text{ M/s}$$
- (D) $$0.2000 \text{ M/s}$$

**Answer: (A)** Calculating the slope of the tangent line provides the instantaneous rate. The slope is $$\frac{0.30 - 0.50}{50 - 0} = -0.0040 \text{ M/s}$$, and the rate of disappearance is the magnitude of this slope.

### Question 9

For a first-order reaction, a plot of $$\ln[\text{A}]$$ versus time is a straight line. The line passes through the points $$(0 \text{ s}, -0.50)$$ and $$(100 \text{ s}, -2.50)$$. What is the value of the rate constant $$k$$ for this reaction?

- (A) $$0.020 \text{ s}^{-1}$$
- (B) $$0.025 \text{ s}^{-1}$$
- (C) $$0.050 \text{ s}^{-1}$$
- (D) $$2.000 \text{ s}^{-1}$$

**Answer: (A)** Identifying the slope of the linearized plot yields the rate constant. For a first-order reaction, the slope of $$\ln[\text{A}]$$ vs. time equals $$-k$$. The slope is $$\frac{-2.50 - (-0.50)}{100} = -0.020$$, so $$k = 0.020 \text{ s}^{-1}$$.

### Question 10

Molecular kinetic energy distributions were measured at two temperatures, $$T_1$$ and $$T_2$$. The distribution at $$T_2$$ is broader, and its maximum occurs at a higher kinetic energy than the maximum at $$T_1$$. Which conclusion is supported by these observations?

- (A) $$T_2 > T_1$$, causing a higher reaction rate
- (B) $$T_2 < T_1$$, causing a lower reaction rate
- (C) $$T_2 > T_1$$, causing a lower reaction rate
- (D) $$T_2 < T_1$$, causing a higher reaction rate

**Answer: (A)** Interpreting the Maxwell-Boltzmann distribution shape reveals the temperature relationship. A flatter curve shifted to higher energies indicates a higher temperature ($$T_2 > T_1$$), which increases the fraction of molecules with energy exceeding $$E_a$$, thus increasing the rate.

## Review the Unit

- [5.1 Reaction Rates](/ap-chem/unit-5/reaction-rates/study-guide/4V94d3BwjoPaOOyQtDKQ)
- [5.2 Introduction to Rate Law](/ap-chem/unit-5/intro-rate-law/study-guide/oq5mJS35IadrTLHLjdqZ)
- [5.3 Concentration Changes Over Time](/ap-chem/unit-5/concentration-changes-over-time/study-guide/Owtcz3zbxFZXsPI7YfwJ)
- [5.4 Elementary Reactions](/ap-chem/unit-5/elementary-reactions/study-guide/SPsFzzECb4aCre0wFrGg)
- [5.5 Collision Model](/ap-chem/unit-5/collision-model/study-guide/rvpVG6AlhGU9AfTvkCdv)
- [5.6 Reaction Energy Profile](/ap-chem/unit-5/reaction-energy-profile/study-guide/RF1B5UBHtCp0qgt8ayp3)
- [5.7 Introduction to Reaction Mechanisms](/ap-chem/unit-5/intro-reaction-mechanisms/study-guide/ATIcHMtAfJw4fOwFzDGK)
- [5.8 Reaction Mechanism and Rate Law](/ap-chem/unit-5/reaction-mechanism-rate-law/study-guide/4v22KrcnuKsP5QYwBUu6)
- [5.9 Pre-Equilibrium Approximation](/ap-chem/unit-5/steady-state-approximation/study-guide/uIOD7v3PLyx0Uf6RDqXJ)
- [5.10 Multistep Reaction Energy Profile](/ap-chem/unit-5/multistep-reaction-energy-profile/study-guide/f9jHiVcKKI9odrJrUITZ)
- [5.11 Catalysis](/ap-chem/unit-5/catalysts/study-guide/bkTgdolcJRgD7fG434Ru)

## Other Unit Tests

- [Unit 1: Atomic Structure & Properties](/ap-chem/unit-test/1)
- [Unit 2: Compound Structure and Properties](/ap-chem/unit-test/2)
- [Unit 3: Properties of Substances and Mixtures](/ap-chem/unit-test/3)
- [Unit 4: Chemical Reactions](/ap-chem/unit-test/4)
- [Unit 6: Thermochemistry](/ap-chem/unit-test/6)
- [Unit 7: Equilibrium](/ap-chem/unit-test/7)
- [Unit 8: Acids & Bases](/ap-chem/unit-test/8)
- [Unit 9: Thermodynamics and Electrochemistry](/ap-chem/unit-test/9)

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