Kinetics: Master Chemical Reaction Rates and Mechanisms

Question 1

How do catalysts affect chemical reactions?

Accepted Answer

Catalysts provide an alternative reaction pathway with a lower activation energy.

Answer

Catalysts increase the activation energy, slowing down reactions.

Answer

Catalysts increase the concentration of reactants, leading to more frequent collisions and faster reactions.

Answer

Catalysts alter the products formed in reactions.

Question 2

Which technique is not typically used to study reaction rates?

Accepted Answer

Gas chromatography

Answer

Spectrophotometry

Answer

Radioactive tracer techniques

Question 3

In the reaction $2A + B → C$, the rate law is expressed as rate = $k[A]^2[B]^1$. What is the reaction order with respect to reactant B?

Accepted Answer

1

Answer

0

Answer

2

Question 4

Which of the following does NOT affect the rate of a chemical reaction?

Accepted Answer

Magnetic field strength

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of solids

Question 5

According to collision theory, what factors influence the rate of a chemical reaction?

Accepted Answer

Higher temperature, concentration, and surface area lead to more frequent collisions.

Accepted Answer

The minimum energy needed for a collision to be effective is called the activation energy.

Accepted Answer

Catalysts speed up reactions by lowering the activation energy.

Answer

All collisions between reactant molecules result in a reaction.

Question 6

A solid reactant A decomposes over time, A(s) → Products, in a closed reaction vessel. How does increasing the surface area of the solid reactant A affect the reaction rate?

Accepted Answer

Increases the rate because more reactant molecules are exposed to react.

Answer

Decreases the rate because fewer reactant molecules are exposed to react.

Answer

Does not affect the rate because the reaction is not surface-dependent.

Answer

May increase or decrease the rate, depending on the specific reaction conditions.

Question 7

In the catalytic cracking of butane, C₄H₁₀, what is the primary function of a heterogeneous catalyst?

Accepted Answer

It offers a surface for reactants to adsorb and react on.

Answer

It is consumed during the reaction.

Answer

It raises the reaction's temperature.

Question 8

A reaction with a high activation energy requires:

Accepted Answer

High temperature to proceed at a significant rate

Answer

Low temperature to overcome the energy barrier

Answer

High concentration of reactants to initiate the reaction

Answer

Presence of a catalyst to lower the energy barrier

Question 9

A catalyst speeds up a reaction by providing an alternative pathway with:

Accepted Answer

Lower activation energy

Answer

More frequent collisions

Answer

Higher concentration of reactants

Answer

Different end products

Question 10

Which expression represents a rate law?

Accepted Answer

Rate = k[NO]^2[O2]

Answer

2NO + O2 → 2NO2

Answer

Activation energy = 90 kJ/mol

Answer

Ea >> RT

Question 11

The mechanism of a reaction describes:

Accepted Answer

The stepwise sequence of elementary reactions that lead to the overall reaction

Answer

The reactants and products involved in the reaction

Answer

The energy changes that accompany the reaction

Answer

The rate at which the reaction proceeds

Question 12

The activation energy of a reaction is the minimum amount of energy that must be supplied to:

Accepted Answer

Start the reaction

Answer

Complete the reaction

Answer

Reach the equilibrium state

Answer

Reverse the reaction

Question 13

Which of the following is the rate law for a first-order reaction?

Accepted Answer

Rate = k[A]

Answer

Rate = k[A]^2

Answer

Rate = k[A][B]

Answer

Rate = k[A]^0

Question 14

The half-life of a first-order reaction is:

Accepted Answer

The time it takes for the concentration of reactants to decrease by half

Answer

The time it takes for the concentration of products to increase by half

Answer

The time it takes for the rate of the reaction to decrease by half

Answer

The time it takes for the activation energy to decrease by half

Question 15

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

Volume of the reaction vessel (at constant pressure and temperature)

Answer

Concentration of reactants

Answer

Temperature

Answer

Surface area of solids

Question 16

Which of the following is NOT a characteristic of a catalyst?

Accepted Answer

Changes the products of reaction

Answer

Increases the rate of reaction

Answer

Consumed in the reaction

Answer

Lowers the activation energy of a reaction

Question 17

A reaction has a very low rate constant. What can be concluded about this reaction?

Accepted Answer

It has a high activation energy

Answer

It is likely to be a first-order reaction

Answer

It is likely to be a second-order reaction

Answer

It will occur very quickly

Question 18

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

Accepted Answer

Stopped-flow

Answer

Batch reactor

Answer

Gas chromatography

Answer

Titration

Question 19

What is the key difference between a homogeneous and a heterogeneous reaction?

Accepted Answer

Homogeneous reactions occur in one phase, while heterogeneous reactions occur in two phases

Answer

Homogeneous reactions are always faster than heterogeneous reactions

Answer

Heterogeneous reactions do not require a catalyst, while homogeneous reactions do

Answer

Homogeneous reactions occur in solution, while heterogeneous reactions occur on a surface

Question 20

What represents the order of reaction with respect to [A] if the rate law is given by rate = k[A]^2[B]?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 21

Which reaction mechanism involves a single elementary step?

Accepted Answer

Unimolecular

Answer

Bimolecular

Answer

Termolecular

Answer

Heterogeneous

Question 22

What is the effect of a catalyst on the equilibrium position of a reaction?

Accepted Answer

No effect

Answer

Shifts to the left

Answer

Shifts to the right

Answer

Depends on the catalyst

Question 23

What is the half-life of a first-order reaction that has a rate constant of 0.05 s^-1?

Accepted Answer

14 s

Answer

20 s

Answer

14 min

Answer

20 min

Question 24

What kind of reaction progress curve is observed for a zero-order reaction?

Accepted Answer

Linear

Answer

Exponential

Answer

Parabolic

Answer

Sigmoidal

Question 25

Which technique can be used to investigate rapid reactions?

Accepted Answer

Stopped-flow method

Answer

Titration

Answer

UV-Vis spectroscopy

Answer

Gas chromatography

Question 26

Why is it essential to consider the units of rate constants when comparing reactions?

Accepted Answer

To compare reaction rates

Answer

To identify reaction order

Answer

To determine activation energy

Answer

To predict the equilibrium constant

Question 27

Which of the following mechanisms is most likely for a reaction that is second order with respect to one reactant and first order with respect to another?

Accepted Answer

Elementary bimolecular

Answer

Elementary unimolecular

Answer

Consecutive unimolecular

Answer

Parallel unimolecular

Question 28

Which of the following is a characteristic of a unimolecular reaction?

Accepted Answer

Rate is proportional to the concentration of the reactant raised to the power of 1

Answer

Rate is proportional to the concentration of the reactant raised to the power of 2

Answer

Rate is independent of the concentration of the reactant

Answer

Rate is very slow

Question 29

Which of the following factors does not affect the rate of a chemical reaction?

Accepted Answer

Color of the reactants

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 30

What is the order of a reaction with respect to reactant 'A' with the rate law expression: rate = k[A]^2[B]?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 31

What is the effect of increasing temperature on the number of effective collisions between reactants?

Accepted Answer

Increases

Answer

Decreases

Answer

Remains the same

Answer

Becomes zero

Question 32

What is the mechanism of a reaction that proceeds through a single transition state?

Accepted Answer

Concerted mechanism

Answer

Stepwise mechanism

Answer

Chain mechanism

Answer

Free radical mechanism

Question 33

Which of the following has no direct effect on the reaction rate of a chemical process?

Accepted Answer

Color of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 34

Which of the following best describes the function of a catalyst in a reaction?

Accepted Answer

It decreases the activation energy of the reaction.

Answer

It increases the activation energy of the reaction.

Answer

It is consumed in the reaction.

Answer

It is produced in the reaction.

Question 35

The activation energy of a reaction reflects the

Accepted Answer

Minimum amount of energy required to initiate a reaction.

Answer

Maximum amount of energy released during a reaction.

Answer

Free energy change between reactants and products.

Answer

Rate of the reaction.

Question 36

Which of the following reactions would release heat into the surroundings?

Accepted Answer

Exothermic

Answer

Endothermic

Answer

Adiabatic

Answer

Isothermal

Question 37

The half-life of a radioactive substance represents the time needed for

Accepted Answer

Half of the substance to decay.

Answer

All of the substance to decay.

Answer

One quarter of the substance to decay.

Answer

One eighth of the substance to decay.

Question 38

Characterize a homogeneous reaction.

Accepted Answer

Takes place within a single phase.

Answer

Takes place within two phases.

Answer

Takes place within three phases.

Answer

Takes place within four phases.

Question 39

What does a reaction mechanism describe?

Accepted Answer

A step-by-step sequence of elementary reactions.

Answer

A mathematical equation representing the rate of a reaction.

Answer

A list of reactants and products involved in a reaction.

Answer

A graphical representation of concentration changes over time.

Question 40

The Arrhenius equation is primarily used to calculate the

Accepted Answer

Activation energy of a reaction.

Answer

Rate constant of a reaction.

Answer

Half-life of a reaction.

Answer

Equilibrium constant of a reaction.

Question 41

Which of the following variables has no influence on the rate of a chemical reaction?

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 42

In a first-order reaction, the half-life is 20 minutes. Determine the rate constant for the reaction.

Accepted Answer

3.47 x 10^-3 s^-1

Answer

3.47 x 10^-2 s^-1

Answer

3.47 x 10^-1 s^-1

Answer

0.347 s^-1

Question 43

Define activation energy in a chemical reaction.

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The maximum energy released by a reaction

Answer

The difference in energy between reactants and products

Answer

The rate of a reaction

Question 44

How does a catalyst affect the activation energy of a reaction?

Accepted Answer

Lowers the activation energy

Answer

Raises the activation energy

Answer

Has no effect on activation energy

Answer

Reverses the activation energy

Question 45

Which of the following is not a characteristic of a spontaneous reaction?

Accepted Answer

Positive change in Gibbs free energy

Answer

Increase in disorder

Answer

Negative change in entropy

Answer

Release of heat

Question 46

Explain the effect of increasing pressure on the rate of a gas-phase reaction.

Accepted Answer

Increases the rate of the reaction

Answer

Decreases the rate of the reaction

Answer

Has no effect on the rate of the reaction

Answer

Reverses the reaction

Question 47

Which of the following factors has no direct impact on the rate of a chemical reaction?

Accepted Answer

Volume of the reaction vessel

Answer

Concentration of reactants

Answer

Temperature

Answer

Presence of a catalyst

Question 48

Which of the following factors does **NOT** affect the rate of a chemical reaction?

Accepted Answer

Volume of the solvent

Answer

Concentration of reactants

Answer

Temperature

Answer

Presence of a catalyst

Question 49

Which of the following is a characteristic of a zero-order reaction?

Accepted Answer

The rate of the reaction is constant

Answer

The rate of the reaction is proportional to the concentration of one reactant

Answer

The rate of the reaction is proportional to the square of the concentration of one reactant

Answer

The rate of the reaction is affected by the presence of a catalyst

Question 50

The activation energy of a reaction is defined as the:

Accepted Answer

Minimum energy required for the reaction to occur

Answer

Maximum energy released by the reaction

Answer

Difference in energy between the reactants and products

Answer

Rate at which the reaction proceeds

Question 51

The mechanism of a reaction refers to:

Accepted Answer

The stepwise sequence of elementary reactions

Answer

The rate law for the reaction

Answer

The equilibrium constant for the reaction

Answer

The activation energy for the reaction

Question 52

Which of the following is a characteristic of a unimolecular reaction?

Accepted Answer

It involves only one reactant molecule

Answer

It is always a first-order reaction

Answer

It is always a second-order reaction

Answer

It is always a third-order reaction

Question 53

What is the minimum energy required for a reaction with an activation energy of 100 kJ/mol to occur?

Accepted Answer

100 kJ/mol

Answer

50 kJ/mol

Answer

200 kJ/mol

Question 54

A first-order reaction has a half-life of 100 seconds. What is the rate constant for the reaction?

Accepted Answer

0.00693 s^-1

Answer

0.01 s^-1

Answer

0.001 s^-1

Answer

0.1 s^-1

Question 55

Which of the following methods will NOT increase the rate of a reaction?

Accepted Answer

Lowering the surface area of reactants

Answer

Increasing the temperature

Answer

Adding a catalyst

Answer

Increasing the concentration of reactants

Question 56

What is the rate law for a reaction that is second-order with respect to one reactant and first-order with respect to another reactant?

Accepted Answer

Rate = k[A]^2[B]

Answer

Rate = k[A]^2

Answer

Rate = k[A][B]

Answer

Rate = k[B]

Question 57

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

The color of the reactants

Answer

The temperature

Answer

The concentration of the reactants

Answer

The presence of a catalyst

Question 58

Which of the following is a characteristic of a first-order reaction?

Accepted Answer

The rate is proportional to the concentration of one reactant.

Answer

The rate is proportional to the product of the concentrations of two reactants.

Answer

The rate is proportional to the square of the concentration of one reactant.

Question 59

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 a reaction.

Question 60

Which equation represents the rate law for a first-order reaction?

Accepted Answer

Rate = k[A]

Answer

Rate = k[A]^2

Answer

Rate = k[A][B]

Answer

Rate = k/[A]

Question 61

What is the activation energy of a reaction?

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The energy released during a reaction

Answer

The rate constant for a reaction

Question 62

Which of the following methods is used to determine the order of a reaction?

Accepted Answer

Measuring the initial rates of reaction at different reactant concentrations

Answer

Using a catalyst

Answer

Measuring the equilibrium constant

Answer

Measuring the activation energy

Question 63

What is the relationship between temperature and the rate of a chemical reaction, according to the Arrhenius equation?

Accepted Answer

Increasing temperature increases the reaction rate

Answer

Increasing temperature decreases the reaction rate

Answer

Decreasing temperature increases the reaction rate

Answer

Temperature has no effect on reaction rate

Question 64

Which assumption of the collision theory states that only a specific type of collision leads to a reaction?

Accepted Answer

Effective collisions

Answer

Reaction rate is directly proportional to reactant concentration

Answer

Reaction rate is inversely proportional to activation energy

Answer

All collisions are effective