CHEM134 Practice Exam 7 Chemical
Kinetics Practice Exam Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. Which statement best describes the primary focus of chemical
kinetics?
A. Determining the equilibrium composition of a reaction
B. Determining the atomic masses of the reactants
C. Studying the rates of chemical reactions and the factors that affect
them
D. Determining whether a compound is ionic or molecular
Answer: C. Studying the rates of chemical reactions and the factors
that affect them
Rationale: Chemical kinetics examines how quickly chemical
reactions occur and how reaction rates are influenced by factors such
as concentration, temperature, surface area, and catalysts.
Thermodynamics addresses whether a process is energetically
favorable, while equilibrium focuses on the relative amounts of
reactants and products at equilibrium. Therefore, studying reaction
rates is the defining purpose of kinetics.
2. For the reaction A → products, the average reaction rate can be
expressed using which quantity?
,A. The change in concentration of A divided by the change in time, with
a negative sign
B. The equilibrium constant divided by temperature
C. The activation energy multiplied by time
D. The concentration of A multiplied by time
Answer: A. The change in concentration of A divided by the change
in time, with a negative sign
Rationale: Because reactant concentration decreases as a reaction
proceeds, the rate based on reactant A is written as −Δ[A]/Δt. The
negative sign ensures that the reaction rate is reported as a positive
quantity. For products, concentration increases, so their rate
expression is positive Δ[product]/Δt.
3. A reaction consumes reactant at a rate of 0.020 M/s. What does this
value represent?
A. The reaction requires 0.020 seconds to reach equilibrium
B. The reactant concentration decreases by 0.020 mol/L every second
C. The reaction produces 0.020 mol of product per reaction
D. The activation energy is 0.020 kJ/mol
Answer: B. The reactant concentration decreases by 0.020 mol/L
every second
Rationale: A rate of 0.020 M/s means that the concentration changes
by 0.020 mol/L for each second under the specified conditions. If the
value refers to a reactant being consumed, its concentration decreases
at that rate. The units M/s are equivalent to mol L⁻¹ s⁻¹ and directly
describe concentration change per unit time.
4. Which factor generally increases the rate of a chemical reaction?
,A. Decreasing the frequency of molecular collisions
B. Lowering the temperature in every reaction
C. Removing all reactant particles from contact
D. Increasing the concentration of a gaseous reactant
Answer: D. Increasing the concentration of a gaseous reactant
Rationale: Increasing the concentration of a reactant generally
increases the number of particles present in a given volume. This
increases collision frequency and can increase the number of
successful collisions per unit time. Temperature, surface area, and
catalysts can also influence reaction rates, but increasing reactant
concentration is a common direct method of increasing collision
frequency.
5. Why does increasing temperature usually increase reaction rate?
A. It increases the fraction of molecules possessing sufficient energy to
overcome activation energy
B. It eliminates the activation energy completely
C. It changes every reaction into an exothermic reaction
D. It necessarily increases the equilibrium constant
Answer: A. It increases the fraction of molecules possessing
sufficient energy to overcome activation energy
Rationale: Raising temperature increases the average kinetic energy of
particles and, more importantly, increases the fraction of molecules
with energy at or above the activation energy. Consequently, more
collisions can become successful reactions. Temperature does not
eliminate activation energy, and it does not necessarily increase the
equilibrium constant because equilibrium constants depend on
thermodynamic factors.
, 6. Which statement correctly describes activation energy?
A. The energy released after equilibrium is reached
B. The minimum energy required for reactant particles to undergo a
successful reaction
C. The total energy contained in all products
D. The energy difference between two equilibrium concentrations
Answer: B. The minimum energy required for reactant particles to
undergo a successful reaction
Rationale: Activation energy, Ea, is the minimum energy barrier that
reacting particles must overcome for a reaction to proceed through its
transition state. A reaction may be thermodynamically favorable and
still proceed slowly if its activation energy is large. Catalysts accelerate
reactions by providing an alternative pathway with lower activation
energy.
7. Which collision is most likely to result in a chemical reaction?
A. One involving particles with insufficient energy and incorrect
orientation
B. One involving particles moving slowly but having random orientation
C. One involving particles with sufficient energy and appropriate
orientation
D. One involving particles that never come into contact
Answer: C. One involving particles with sufficient energy and
appropriate orientation
Rationale: Collision theory states that particles must collide with
sufficient energy and an appropriate orientation to produce a
successful reaction. Merely colliding is not enough. If the collision
energy is below the activation energy or the molecules are incorrectly
Kinetics Practice Exam Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. Which statement best describes the primary focus of chemical
kinetics?
A. Determining the equilibrium composition of a reaction
B. Determining the atomic masses of the reactants
C. Studying the rates of chemical reactions and the factors that affect
them
D. Determining whether a compound is ionic or molecular
Answer: C. Studying the rates of chemical reactions and the factors
that affect them
Rationale: Chemical kinetics examines how quickly chemical
reactions occur and how reaction rates are influenced by factors such
as concentration, temperature, surface area, and catalysts.
Thermodynamics addresses whether a process is energetically
favorable, while equilibrium focuses on the relative amounts of
reactants and products at equilibrium. Therefore, studying reaction
rates is the defining purpose of kinetics.
2. For the reaction A → products, the average reaction rate can be
expressed using which quantity?
,A. The change in concentration of A divided by the change in time, with
a negative sign
B. The equilibrium constant divided by temperature
C. The activation energy multiplied by time
D. The concentration of A multiplied by time
Answer: A. The change in concentration of A divided by the change
in time, with a negative sign
Rationale: Because reactant concentration decreases as a reaction
proceeds, the rate based on reactant A is written as −Δ[A]/Δt. The
negative sign ensures that the reaction rate is reported as a positive
quantity. For products, concentration increases, so their rate
expression is positive Δ[product]/Δt.
3. A reaction consumes reactant at a rate of 0.020 M/s. What does this
value represent?
A. The reaction requires 0.020 seconds to reach equilibrium
B. The reactant concentration decreases by 0.020 mol/L every second
C. The reaction produces 0.020 mol of product per reaction
D. The activation energy is 0.020 kJ/mol
Answer: B. The reactant concentration decreases by 0.020 mol/L
every second
Rationale: A rate of 0.020 M/s means that the concentration changes
by 0.020 mol/L for each second under the specified conditions. If the
value refers to a reactant being consumed, its concentration decreases
at that rate. The units M/s are equivalent to mol L⁻¹ s⁻¹ and directly
describe concentration change per unit time.
4. Which factor generally increases the rate of a chemical reaction?
,A. Decreasing the frequency of molecular collisions
B. Lowering the temperature in every reaction
C. Removing all reactant particles from contact
D. Increasing the concentration of a gaseous reactant
Answer: D. Increasing the concentration of a gaseous reactant
Rationale: Increasing the concentration of a reactant generally
increases the number of particles present in a given volume. This
increases collision frequency and can increase the number of
successful collisions per unit time. Temperature, surface area, and
catalysts can also influence reaction rates, but increasing reactant
concentration is a common direct method of increasing collision
frequency.
5. Why does increasing temperature usually increase reaction rate?
A. It increases the fraction of molecules possessing sufficient energy to
overcome activation energy
B. It eliminates the activation energy completely
C. It changes every reaction into an exothermic reaction
D. It necessarily increases the equilibrium constant
Answer: A. It increases the fraction of molecules possessing
sufficient energy to overcome activation energy
Rationale: Raising temperature increases the average kinetic energy of
particles and, more importantly, increases the fraction of molecules
with energy at or above the activation energy. Consequently, more
collisions can become successful reactions. Temperature does not
eliminate activation energy, and it does not necessarily increase the
equilibrium constant because equilibrium constants depend on
thermodynamic factors.
, 6. Which statement correctly describes activation energy?
A. The energy released after equilibrium is reached
B. The minimum energy required for reactant particles to undergo a
successful reaction
C. The total energy contained in all products
D. The energy difference between two equilibrium concentrations
Answer: B. The minimum energy required for reactant particles to
undergo a successful reaction
Rationale: Activation energy, Ea, is the minimum energy barrier that
reacting particles must overcome for a reaction to proceed through its
transition state. A reaction may be thermodynamically favorable and
still proceed slowly if its activation energy is large. Catalysts accelerate
reactions by providing an alternative pathway with lower activation
energy.
7. Which collision is most likely to result in a chemical reaction?
A. One involving particles with insufficient energy and incorrect
orientation
B. One involving particles moving slowly but having random orientation
C. One involving particles with sufficient energy and appropriate
orientation
D. One involving particles that never come into contact
Answer: C. One involving particles with sufficient energy and
appropriate orientation
Rationale: Collision theory states that particles must collide with
sufficient energy and an appropriate orientation to produce a
successful reaction. Merely colliding is not enough. If the collision
energy is below the activation energy or the molecules are incorrectly
