Chemical Kinetics: Master Reaction Rates and Mechanisms

Question 1

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

Accepted Answer

Magnetic field

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of solid reactants

Question 2

In chemical reactions, what is the definition of activation energy?

Accepted Answer

The minimum energy level molecules must reach to undergo a specific chemical reaction.

Answer

The total energy released during a chemical reaction.

Answer

The energy difference between reactants and products in a chemical reaction.

Answer

The energy required for a reaction to reach equilibrium.

Question 3

Which factor does NOT affect 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 4

Which factor would cause a significant decrease in the reaction rate for the reaction A + B -> C?

Accepted Answer

Lowering the temperature of the reaction

Answer

Increasing the concentration of reactant A

Answer

Adding a catalyst to the reaction mixture

Answer

Using a solvent with a higher polarity

Question 5

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

Accepted Answer

Color of the reaction mixture

Answer

Temperature

Answer

Reactant concentration

Answer

Surface area of solid reactants

Question 6

Which factor will increase the rate of a chemical reaction?

Accepted Answer

Raising the concentration of the reactants

Answer

Lowering the temperature

Answer

Reducing the surface area of the reactants

Answer

Introducing an inert gas to the reaction mixture

Question 7

Which factors commonly affect the rate of a chemical reaction?

Accepted Answer

Temperature

Accepted Answer

Concentration

Accepted Answer

Surface area

Answer

Magnetic field

Question 8

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

Accepted Answer

Addition of an inert gas

Answer

Temperature

Answer

Presence of a catalyst

Answer

Surface area of reactants (in heterogeneous reactions)

Question 9

Which factor does NOT directly affect the rate of a chemical reaction?

Accepted Answer

Volume of the reaction container

Answer

Concentrations of the reactants

Answer

Temperature

Answer

Nature of the reactants (e.g., size, shape)

Question 10

Which factor does **NOT** influence the reaction rate of a chemical reaction?

Accepted Answer

Identity of the solvent

Answer

Concentration of reactants

Answer

Temperature

Answer

Presence of a Catalyst

Question 11

In a reaction mechanism with multiple elementary steps, which characteristic differentiates the slowest step from the others?

Accepted Answer

Highest activation energy

Answer

Lowest activation energy

Answer

Lowest reactant concentration

Question 12

How does increasing the temperature affect the rate of a chemical reaction?

Accepted Answer

Increases the reaction rate

Answer

Decreases the reaction rate

Answer

Has no effect on the reaction rate

Answer

Stops the reaction completely

Question 13

A catalyst lowers the activation energy in a reaction pathway. What is the main effect of this?

Accepted Answer

The reaction rate increases.

Answer

The equilibrium position of the reaction changes.

Answer

The concentration of reactants increases.

Question 14

In a reaction mechanism, what immediately follows the formation of an intermediate complex?

Accepted Answer

Transition state

Answer

Rate-limiting step

Answer

Release of products

Answer

Activation of reactants

Question 15

In a chemical reaction, the activation energy represents the minimum energy needed for reactants to transform. How does increasing the activation energy impact the reaction rate?

Accepted Answer

Decreases the reaction rate

Answer

Increases the reaction rate

Answer

No effect on the reaction rate

Question 16

Based on the collision theory, which factor **decreases** the reaction rate?

Accepted Answer

Decreasing the temperature of reactants

Answer

Increasing the surface area of reactants

Answer

Increasing the concentration of reactants

Question 17

Consider the reaction: A + B --> C. Its rate law is rate = k[A]^2[B]. Which mechanism is most likely?

Accepted Answer

Two-step mechanism with an intermediate

Answer

One-step, concerted mechanism

Answer

Chain mechanism with free radicals

Answer

Unimolecular mechanism

Question 18

What is the correct unit for expressing the rate of a reaction, which is defined as the change in concentration of reactant or product per unit time?

Accepted Answer

M s-1

Answer

M-1 s

Answer

s-1

Answer

M L-1

Question 19

In the rate law rate = k[A][B]^2, what is the order of the reaction with respect to reactant B?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 20

A chemical reaction follows the rate law: rate = k[A][B]². What is the order of the reaction with respect to reactant B?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 21

In a chemical reaction, how does the addition of a catalyst affect the reaction?

Accepted Answer

Provides an alternative pathway, making the reaction faster.

Answer

Increases the activation energy, making the reaction slower.

Answer

Decreases the number of collisions between reactants, making the reaction slower.

Answer

Consumes the products of the reaction, making the reaction proceed in the forward direction.

Question 22

How does the reaction rate typically change as the concentration of reactants increases?

Accepted Answer

The rate increases proportionally to the concentration of each reactant raised to its order.

Answer

The rate decreases as the concentration of the reactant with the highest concentration increases.

Answer

The rate remains constant regardless of the concentration of the reactants.

Answer

The rate is always slower when the reactants are in a solid state.

Question 23

Which of the following factors does **not** affect 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 24

The rate law for a reaction is rate = k[A]^2[B]. What is the order of the reaction with respect to A?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 25

The activation energy of a reaction is 100 kJ/mol. If the temperature is doubled, by what factor does the rate constant increase?

Accepted Answer

Increases the rate constant by a factor of 16

Answer

Doubles the rate constant

Answer

Increases the rate constant by a factor of 4

Answer

Increases the rate constant by a factor of 8

Question 26

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 and increases the rate

Answer

A substance that is consumed in a reaction and decreases the rate

Question 27

The mechanism of a reaction involves the formation of an intermediate. What is the purpose of the intermediate?

Accepted Answer

To provide an alternative pathway for the reaction to proceed

Answer

To increase the activation energy of the reaction

Answer

To decrease the rate of the reaction

Answer

To consume the reactants

Question 28

What is the half-life of a radioactive isotope?

Accepted Answer

The time it takes for half of the isotope to decay

Answer

The time it takes for the isotope to completely decay

Answer

The amount of isotope remaining after half of its half-life has passed

Answer

The rate constant for the decay of the isotope

Question 29

Which of the following techniques can be used to study very fast reactions?

Accepted Answer

Stopped-flow spectrophotometry

Answer

Nuclear magnetic resonance (NMR) spectroscopy

Answer

Gas chromatography-mass spectrometry (GC-MS)

Answer

High-performance liquid chromatography (HPLC)

Question 30

Which of the following is the rate law expression for a  second-order reaction with respect to reactant A?

Accepted Answer

rate = k[A]^2

Answer

rate = k[A]

Answer

rate = k[A][B]

Answer

rate = k[A]^2[B]

Question 31

How does temperature typically affect reaction rates?

Accepted Answer

Increases exponentially

Answer

Decreases exponentially

Answer

Remains constant

Answer

Can increase or decrease depending on the reaction

Question 32

Which of the following is a catalyst?

Accepted Answer

A substance that lowers the activation energy of a reaction

Answer

A substance that increases the activation energy of a reaction

Answer

A substance that is consumed in a reaction

Answer

A substance that is produced in a reaction

Question 33

What is the activation energy of a reaction?

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The energy released when a reaction occurs

Answer

The rate constant of a reaction

Answer

The order of a reaction

Question 34

Which of the following reactions is likely to have the fastest reaction rate?

Accepted Answer

A reaction with a low activation energy and high temperature

Answer

A reaction with a high activation energy and high temperature

Answer

A reaction with a low activation energy and low temperature

Answer

A reaction with a high activation energy and low temperature

Question 35

What is the half-life of a reactant in a first-order reaction?

Accepted Answer

The time it takes for half of the reactant to be consumed

Answer

The time it takes for the reaction to complete

Answer

The time it takes for the concentration of the reactant to reach zero

Answer

The time it takes for the rate of the reaction to halve

Question 36

What is the rate-determining step of a reaction?

Accepted Answer

The slowest step in a reaction mechanism

Answer

The fastest step in a reaction mechanism

Answer

The step that releases the most energy

Answer

The step that forms the most stable intermediate

Question 37

Which of the following is a key component of a rate law expression?

Accepted Answer

Rate constant of the reaction

Answer

Stoichiometry of the balanced reaction

Answer

Mechanism of the reaction

Answer

Equilibrium constant of the reaction

Question 38

For a first-order reaction, the half-life is defined as the time required for:

Accepted Answer

The concentration of the reactant to decrease by half

Answer

The concentration of the product to double

Answer

The rate of the reaction to decrease by half

Answer

The activation energy of the reaction to decrease by half

Question 39

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

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants

Answer

Nature of the catalyst

Question 40

According to the Arrhenius equation, the rate constant (k) of a reaction is:

Accepted Answer

Exponentially proportional to the temperature (T)

Answer

Directly proportional to the temperature (T)

Answer

Inversely proportional to the temperature (T)

Answer

Independent of the temperature (T)

Question 41

Which type of reaction mechanism typically involves the lowest activation energy?

Accepted Answer

Single-step elementary reaction

Answer

Two-step mechanism involving an intermediate

Answer

Three-step mechanism involving two intermediates

Answer

Chain reaction

Question 42

Consider the reaction A + 2B -> C. If the rate law for this reaction is rate = k[A][B]^2, what is the overall order of the reaction?

Accepted Answer

3

Answer

1

Answer

2

Answer

4

Question 43

The activation energy (Ea) of a reaction is the minimum amount of energy required to:

Accepted Answer

Reach the transition state of the reaction

Answer

Break bonds in the reactants

Answer

Form bonds in the products

Answer

Complete the reaction

Question 44

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

Accepted Answer

It is consumed in the reaction

Answer

It is in the same phase as the reactants

Answer

It lowers the activation energy of the reaction

Answer

It is specific for a particular reaction or type of reaction

Question 45

The rate law for a reaction is expressed as: Rate = k[A]ⁿ[B]^m. What is the overall order of the reaction with respect to A and B?

Accepted Answer

n + m

Answer

n - m

Answer

n * m

Answer

n / m

Question 46

Which of the following reaction mechanisms typically involves a high activation energy?

Accepted Answer

Chain mechanism

Answer

One-step mechanism

Answer

Two-step mechanism

Answer

Heterogeneous mechanism

Question 47

How does pressure affect the rate of a gas-phase reaction?

Accepted Answer

Pressure increases the rate of a gas-phase reaction by increasing the number of collisions between molecules.

Answer

Pressure has no effect on the rate of a gas-phase reaction.

Answer

Pressure decreases the rate of a gas-phase reaction by decreasing the number of collisions between molecules.

Answer

Pressure has a small effect on the rate of a gas-phase reaction.

Question 48

Which of the following is NOT a factor that affects reaction rates in chemical kinetics?

Accepted Answer

Color of reactants

Answer

Concentration of reactants

Answer

Temperature

Answer

Presence of a catalyst

Question 49

Consider the rate law: rate = k[A]^2[B]. What is the overall order of the reaction?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 50

An enzyme-catalyzed reaction exhibits a bell-shaped curve when reaction rate is plotted against substrate concentration. The most likely explanation is:

Accepted Answer

Enzyme active sites are saturated at high substrate concentrations

Answer

Enzyme denatures at high substrate concentrations

Answer

Substrate inhibits the enzyme at high concentrations

Question 51

Which of the following statements about activation energy is correct?

Accepted Answer

It is the minimum energy required for a reaction to occur

Answer

It is the energy difference between the reactants and products

Answer

It is always negative

Answer

It is unaffected by temperature

Question 52

Which of the following characteristics applies to unimolecular reactions?

Accepted Answer

Rate is independent of reactant concentration

Answer

Rate is first-order

Answer

Rate is second-order

Answer

Rate is third-order

Question 53

Which of the following factors does NOT affect 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 54

Which factor does NOT affect reaction rates?

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 55

Define the rate-determining step in a multi-step reaction.

Accepted Answer

The step with the highest activation energy.

Answer

The step that occurs first.

Answer

The step that occurs last.

Answer

The step that produces the most product.

Question 56

What is the half-life of a reaction?

Accepted Answer

The time it takes for half of the reactants to be consumed.

Answer

The time it takes for the concentration of the products to double.

Answer

The time it takes for the reaction to reach completion.

Answer

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

Question 57

A catalyst speeds up a reaction by:

Accepted Answer

Providing an alternative reaction pathway with a lower activation energy

Answer

Increasing the concentration of reactants

Answer

Decreasing the temperature of the reaction

Answer

Removing products from the reaction

Question 58

The rate law for a reaction is rate = k[A]^2[B]. What is the order of the reaction with respect to reactant A?

Accepted Answer

2

Answer

0

Answer

1

Answer

3

Question 59

The Arrhenius equation relates the rate constant of a reaction to temperature. Which term in the Arrhenius equation represents activation energy?

Accepted Answer

Ea

Answer

A

Answer

B

Answer

R

Question 60

Which of the following is the definition of a catalyst?

Accepted Answer

A substance that participates in a reaction and regenerates at the end of the reaction, thereby altering the reaction rate.

Answer

A substance that impedes a reaction.

Answer

A substance that is consumed during a reaction.

Answer

A substance that is a product of a reaction.

Question 61

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

Accepted Answer

Color of the reactants

Answer

Temperature

Answer

Surface area of the reactants

Answer

Concentration of the reactants

Question 62

For a reaction with rate law rate = k[A]^2[B], what is the order of the reaction with respect to A?

Accepted Answer

2

Answer

-1

Answer

0.5

Answer

1

Question 63

Which of the following is an example of a homogeneous catalyst?

Accepted Answer

Enzyme

Answer

Heterogeneous catalyst

Answer

Activated carbon

Answer

Metal surface

Question 64

How does increasing the temperature generally affect the rate of a reaction?

Accepted Answer

Increases the rate

Answer

Decreases the rate

Answer

Does not affect the rate