Kinetics: Reaction Rates and Factors Influencing Them

Question 1

How does particle size influence the rate of a chemical reaction?

Accepted Answer

Smaller particles react faster due to increased surface area.

Answer

Larger particles react faster due to increased surface area.

Answer

Particle size has no impact on reaction rate.

Answer

Smaller particles react slower due to decreased surface area.

Question 2

The activation energy of a reaction is the minimum amount of energy required for the:

Accepted Answer

Reactants to reach the transition state

Answer

Products to form

Answer

Reactants to collide

Answer

Reaction to complete

Question 3

Which of the following reactions is a **homogeneous reaction**?

Accepted Answer

Reaction between aqueous sodium chloride and silver nitrate

Answer

Reaction between hydrogen and oxygen

Answer

Reaction between solid sodium and chlorine gas

Answer

Reaction between magnesium and hydrochloric acid

Question 4

The rate law for a reaction is:

Accepted Answer

An expression that relates the rate of reaction to the concentrations of reactants

Answer

A mathematical equation that describes the mechanism of a reaction

Answer

A graphical representation of the change in reactant concentrations over time

Answer

A table that summarizes the experimental data on reaction rates

Question 5

The order of a reaction is:

Accepted Answer

The exponent of the concentration term in the rate law

Answer

The sum of the coefficients in the balanced chemical equation

Answer

The number of times the reaction must occur to reach completion

Answer

The temperature at which the reaction proceeds fastest

Question 6

A catalyst:

Accepted Answer

Provides an alternative pathway for the reaction

Answer

Increases the activation energy of a reaction

Answer

Decreases the number of collisions between reactants

Answer

Consumes one of the reactants

Question 7

The half-life of a radioactive isotope is:

Accepted Answer

The time it takes for half of the isotope to decay

Answer

The time it takes for the isotope to become completely stable

Answer

The amount of isotope that remains after one decay event

Answer

The rate constant for the decay process

Question 8

Which of the following reactions is a **unimolecular reaction**?

Accepted Answer

Decomposition of ozone

Answer

Reaction between hydrogen and iodine

Answer

Reaction between sodium hydroxide and hydrochloric acid

Answer

Reaction between carbon monoxide and oxygen

Question 9

The activation energy of a reaction represents the:

Accepted Answer

Minimum energy required for a reaction to occur

Answer

Maximum energy released by a reaction

Answer

Rate at which a reaction proceeds

Answer

Equilibrium constant for a reaction

Question 10

A catalyst:

Accepted Answer

Decreases the activation energy of a reaction

Answer

Increases the activation energy of a reaction

Answer

Changes the products of a reaction

Answer

Does not affect the rate of a reaction

Question 11

In a heterogeneous reaction:

Accepted Answer

Reactants and products are in different phases

Answer

Reactants and products are in the same phase

Answer

The reaction rate is independent of surface area

Answer

The reaction rate is inversely proportional to temperature

Question 12

The rate law for a reaction is determined through:

Accepted Answer

Experimentation and data analysis

Answer

Theoretical calculations

Answer

The balanced chemical equation

Answer

The activation energy of the reaction

Question 13

Which of the following is NOT an application of kinetics?

Accepted Answer

Determining the age of archaeological artifacts

Answer

Designing industrial chemical processes

Answer

Predicting the shelf life of food

Answer

Understanding biochemical reactions in living organisms

Question 14

The order of a reaction with respect to a reactant is:

Accepted Answer

The power to which the concentration of the reactant is raised in the rate law

Answer

The number of moles of the reactant consumed in the reaction

Answer

The activation energy of the reaction

Answer

The equilibrium constant for the reaction

Question 15

A zero-order reaction has a rate law expression that is:

Accepted Answer

Independent of concentration

Answer

Linear with respect to concentration

Answer

Quadratic with respect to concentration

Answer

Exponential with respect to concentration

Question 16

Which of the following techniques is used to study fast reactions?

Accepted Answer

Stopped-flow method

Answer

Potentiometry

Answer

Conductometry

Answer

Titration

Question 17

The rate law for a reaction is established by:

Accepted Answer

Measuring the rate of change of reactant or product concentrations over time

Answer

Guesswork and trial and error

Answer

Balancing the chemical equation

Answer

Predicting the products of the reaction

Question 18

A catalyst:

Accepted Answer

Lowers the activation energy of the reaction, providing an alternative pathway

Answer

Is consumed in the reaction

Answer

Increases the activation energy of the reaction

Answer

Has no effect on the reaction rate

Question 19

The activation energy of a reaction is the:

Accepted Answer

Minimum energy required for a reaction to occur

Answer

Maximum energy released in a reaction

Answer

Energy difference between reactants and products

Answer

Rate at which the reaction proceeds

Question 20

A reaction proceeds via a two-step mechanism. The first step is fast and reversible, while the second step is slow and irreversible. Which of the following statements is true?

Accepted Answer

The rate-determining step is the second step.

Answer

The rate-determining step is the first step.

Answer

The overall rate law will be first order.

Answer

The overall rate law will be second order.

Question 21

A catalyst is a substance that:

Accepted Answer

Decreases the activation energy of a reaction.

Answer

Increases the activation energy of a reaction.

Answer

Changes the products of a reaction.

Answer

Is consumed in a reaction.

Question 22

The half-life of a reaction is the time it takes for:

Accepted Answer

The concentration of reactants to decrease by half.

Answer

The concentration of products to increase by half.

Answer

The rate of the reaction to decrease by half.

Answer

The temperature of the reaction to increase by half.

Question 23

Which of the following reactions represents a unimolecular reaction?

Accepted Answer

N2O5(g) → 2NO2(g) + O2(g)

Answer

2NO(g) + O2(g) → 2NO2(g)

Answer

CH3CH2Br(g) → CH2=CH2(g) + HBr(g)

Answer

2H2(g) + O2(g) → 2H2O(g)

Question 24

A catalyst in a chemical reaction:

Accepted Answer

Provides an alternative pathway for the reaction with lower activation energy

Answer

Increases the activation energy of the reaction

Answer

Decreases the concentration of reactants

Answer

Slows down the rate of the reaction

Question 25

The activation energy for a reaction is the:

Accepted Answer

Minimum amount of energy that must be supplied to the reactants for the reaction to occur

Answer

Maximum amount of energy that can be released by the reaction

Answer

Difference in energy between the reactants and the products

Answer

Rate constant for the reaction

Question 26

Which of the following is NOT a method to increase the rate of a reaction?

Accepted Answer

Decreasing the surface area of solid reactants

Answer

Increasing the temperature

Answer

Increasing the concentration of reactants

Answer

Adding a catalyst

Question 27

Kinetics is the study of:

Accepted Answer

Rates and mechanisms of chemical reactions

Answer

Chemical reactions reaching equilibrium

Answer

Energy changes in chemical reactions

Answer

Classification of chemical reactions

Question 28

What is activation energy?

Accepted Answer

The minimum amount of energy required to initiate a reaction

Answer

The difference in energy between the reactants and products

Answer

The rate constant of a reaction

Answer

The equilibrium constant of a reaction

Question 29

Which of the following is a catalyst?

Accepted Answer

A substance that increases the rate of a reaction without being consumed

Answer

A substance that decreases the rate of a reaction without being consumed

Answer

A substance that is consumed in the reaction

Answer

A substance that is formed in the reaction

Question 30

Classify the reaction between solid iron nails and aqueous copper(II) sulfate solution as either heterogeneous or homogeneous. Explain your choice.

Accepted Answer

Heterogeneous - Reactants are in different phases (solid and liquid)

Answer

Homogeneous - Reactants are in the same phase (both in solution)

Answer

Cannot be determined - Information about the physical states of the reactants is missing

Answer

Depends on temperature - Not relevant to the classification of heterogeneous or homogeneous reactions

Question 31

How does the concentration of reactants influence the rate of a chemical reaction?

Accepted Answer

Increasing reactant concentration accelerates the reaction rate due to increased particle collisions.

Answer

Concentration has no impact on the rate of a chemical reaction.

Answer

Increasing product concentration slows the reaction rate by reducing reactant particle collisions.

Answer

Concentration affects reaction rates only in gases, not in liquids or solids.

Question 32

Enzymes play a crucial role in biochemical reactions. Describe how enzymes act as catalysts, including the mechanisms they employ to speed up these reactions.

Accepted Answer

Enzymes lower the activation energy of reactions, providing an alternative pathway with a lower energy barrier.

Answer

Enzymes increase the activation energy of reactions, slowing down the reaction rate.

Answer

Enzymes do not affect the activation energy of reactions; they simply provide a different pathway for the reaction to occur.

Question 33

Which factor does NOT affect the rate of a heterogeneous reaction?

Accepted Answer

Concentration of reactants in the bulk solution

Answer

Nature of the catalyst

Answer

Concentration of reactants on the surface

Answer

Temperature

Question 34

In a gas phase reaction, which factor is likely to increase the rate of reaction?

Accepted Answer

Higher average kinetic energy of the reactant molecules

Answer

Lower temperature

Answer

Decrease in surface area of reactants

Question 35

Which of the following substances can act as a catalyst in a chemical reaction?

Accepted Answer

Enzyme

Answer

Inert gas

Answer

Pure water

Answer

Solid sodium chloride

Question 36

The rate law of a reaction expresses the relationship between:

Accepted Answer

Rate of reaction and concentrations of reactants

Answer

Equilibrium constant and temperature

Answer

Activation energy and temperature

Question 37

Which of the following units is commonly used to express the rate of a reaction?

Accepted Answer

M/s

Answer

J

Answer

%

Answer

kJ/mol

Question 38

A reaction has a rate constant of 4.0 x 10^-4 s^-1. What is the half-life of the reaction?

Accepted Answer

173 s

Answer

346 s

Answer

693 s

Answer

87 s

Question 39

Which of the following is an example of a unimolecular reaction mechanism?

Accepted Answer

Isomerization

Answer

Addition

Answer

Substitution

Answer

Elimination

Question 40

Which of the following reactions is an example of a homogeneous reaction?

Accepted Answer

The reaction of hydrogen and oxygen gases to form water vapor

Answer

The reaction of zinc metal with copper sulfate solution

Answer

The reaction of calcium carbonate with hydrochloric acid

Question 41

The activation energy of a reaction can be determined by:

Accepted Answer

Measuring the rate of reaction at different temperatures

Answer

Measuring the change in enthalpy of the reaction

Answer

Measuring the equilibrium constant of the reaction

Question 42

A reaction has an activation energy of 120 kJ/mol. What will be the effect of increasing the temperature from 298 K to 313 K on the rate of the reaction?

Accepted Answer

Approximately double the rate

Answer

No significant effect on the rate

Answer

Increase the rate by a factor of 4

Answer

Increase the rate by a factor of 8

Question 43

Which of the following reactions is a heterogeneous reaction?

Accepted Answer

Reaction of solid zinc with dilute hydrochloric acid

Answer

Thermal decomposition of ammonium nitrate

Answer

Reaction of hydrogen and chlorine gases