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AP Chemistry Practice Quiz: Introduction to Rate Law

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

A rate law is a mathematical expression that relates the rate of a reaction to which of the following?

All Questions (12)

A rate law is a mathematical expression that relates the rate of a reaction to which of the following?

A) The concentrations of the products

B) The temperature and pressure of the system

C) The concentrations of the reactants

D) The total time elapsed for the reaction

Correct Answer: C

According to the provided content, 'The rate law expresses the rate of a reaction as proportional to the concentration of each reactant raised to a power.' This directly links the reaction rate to reactant concentrations.

What is the primary purpose of using experimental methods to monitor the amounts of reactants and products over time in a kinetics study?

A) To determine the final equilibrium position of the reaction

B) To identify all possible side products

C) To calculate the thermodynamic favorability of the reaction

D) To determine the rate of the reaction

Correct Answer: D

The provided content states that 'Experimental methods can be used to monitor the amounts of reactants and/or products of a reaction over time and to determine the rate of the reaction.'

For a reaction with the experimentally determined rate law: Rate = k[A]^2[B]^1, what is the reaction order with respect to reactant B?

A) 0

B) 1

C) 2

D) 3

Correct Answer: B

The content specifies that 'The power of each reactant is its reaction order.' In the given rate law, the concentration of reactant B is raised to the power of 1.

Consider the rate law: Rate = k[X]^1[Y]^2. What is the overall order of this reaction?

A) 1

B) 2

C) 3

D) Cannot be determined from the rate law

Correct Answer: C

The overall order of a reaction is 'the sum of the powers' of the reactant concentrations in the rate law. In this case, the overall order is the sum of the order of X (1) and the order of Y (2), which is 1 + 2 = 3.

The value of the rate constant, k, in a rate law expression is known to be significantly dependent on which of the following factors?

A) The initial concentration of reactants

B) The volume of the container

C) The temperature

D) The concentration of products

Correct Answer: C

The provided content explicitly states that the value of the rate constant (k) 'is temperature dependent.'

In the general rate law expression, Rate = k[Reactant]^n, the term 'k' is best described as the:

A) reaction order

B) overall reaction order

C) rate constant

D) reactant concentration

Correct Answer: C

The content defines 'k' as 'the proportionality constant in the rate law,' which is known as the rate constant.

A particular reaction is determined to be third-order overall. If the rate is measured in M/s (molarity per second), what are the units of the rate constant, k?

A) M/s

B) M⁻¹s⁻¹

C) M⁻²s⁻¹

D) s⁻¹

Correct Answer: C

The units of k must make the rate law equation dimensionally consistent. For a third-order reaction (Rate = k[A]³), the units are M/s = (units of k) * (M³). Solving for the units of k gives (M/s) / M³ = M⁻²s⁻¹. The content states that the units of k 'reflect the overall reaction order.'

Which experimental approach involves systematically varying the initial concentrations of reactants to see the effect on the initial reaction rate, thereby determining the order for each reactant?

A) Titration analysis

B) Continuous monitoring

C) Method of Initial Rates

D) Equilibrium constant measurement

Correct Answer: C

The content directly states that 'Comparing initial rates of a reaction (Method of Initial Rates) is a method to determine the order with respect to each reactant.'

For the reaction A → Products, experimental data shows that when the initial concentration of A is tripled, the initial rate of reaction increases by a factor of nine. What is the order of the reaction with respect to A?

A) Zero-order

B) First-order

C) Second-order

D) Third-order

Correct Answer: C

This is an application of the Method of Initial Rates. The rate is proportional to [A] raised to a power (the order, x). So, Rate ∝ [A]^x. When [A] is multiplied by 3, the rate is multiplied by 9. Therefore, 9 = 3^x. The value of x that satisfies this equation is 2, so the reaction is second-order with respect to A.

Consider the following initial rate data for the reaction X + Y → Z: | Experiment | [X] (M) | [Y] (M) | Initial Rate (M/s) | |------------|---------|---------|--------------------| | 1 | 0.10 | 0.10 | 0.005 | | 2 | 0.20 | 0.10 | 0.020 | | 3 | 0.10 | 0.20 | 0.005 | Based on this data, what is the correct rate law expression for the reaction?

A) Rate = k[X][Y]

B) Rate = k[X]²

C) Rate = k[Y]²

D) Rate = k[X]

Correct Answer: B

Using the Method of Initial Rates: Comparing Experiments 1 and 2, [X] doubles while [Y] is constant, and the rate quadruples (0.020/0.005 = 4). This means the reaction is second-order in X (2² = 4). Comparing Experiments 1 and 3, [Y] doubles while [X] is constant, and the rate does not change. This means the reaction is zero-order in Y (2⁰ = 1). Therefore, the rate law is Rate = k[X]²[Y]⁰, which simplifies to Rate = k[X]².

In a rate law, the exponent to which a specific reactant's concentration is raised is formally known as its:

A) rate constant

B) stoichiometric coefficient

C) overall order

D) reaction order

Correct Answer: D

The provided content defines this exponent directly: 'The power of each reactant is its reaction order.'

If a reaction's rate is expressed as Rate = k[X][Y]⁰, how would doubling the concentration of reactant Y affect the overall reaction rate, assuming all other conditions are constant?

A) The rate would be halved

B) The rate would double

C) The rate would not change

D) The rate would quadruple

Correct Answer: C

The reaction order with respect to Y is zero, as indicated by the power of 0. Any number raised to the power of zero is 1. Therefore, the concentration of Y does not influence the rate. The rate law expresses the rate as proportional to the concentration of each reactant raised to a power, and in this case, that power for [Y] is zero.