Kinetics: Reaction Rates and Factors Affecting Them

Question 1

Which of the following does NOT directly 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 (in heterogeneous reactions)

Question 2

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

Accepted Answer

Wavelength of light

Answer

Concentration of reactants

Answer

Temperature

Answer

Surface area of reactants

Question 3

A chemical reaction involves gaseous reactants A and B: $$A(g) + B(g) ---> C(g)$$. Which change would increase the reaction rate?

Accepted Answer

Raising the concentration of reactant A

Answer

Lowering the temperature

Answer

Reducing the surface area of the reactants

Answer

Adding an inert gas to the reaction mixture

Question 4

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

Accepted Answer

Color of the reaction mixture

Answer

Concentration of reactants

Answer

Activation energy

Answer

Presence of a catalyst

Question 5

In a first-order reaction, the reaction rate is directly proportional to the concentration of which species?

Accepted Answer

Reactant undergoing the reaction

Answer

All reactants

Answer

Products

Answer

Catalyst

Question 6

In the transition state theory, which molecular arrangement represents the highest energy point on the reaction coordinate diagram?

Accepted Answer

Transition state

Answer

Reactants

Answer

Products

Question 7

A chemical reaction's half-life is inversely proportional to the square of the initial reactant concentration. What's the reaction order?

Accepted Answer

Second order

Answer

First order

Answer

Third order

Answer

Zero order

Question 8

A student is investigating the reaction between sodium thiosulfate and hydrochloric acid. Which change would increase the reaction rate?

Accepted Answer

Increasing the surface area of the sodium thiosulfate

Answer

Lowering the temperature of the reaction mixture

Answer

Adding a small amount of sodium chloride to the reaction mixture

Question 9

In the Arrhenius equation, how does activation energy (Ea) affect the rate constant (k) at a specific temperature?

Accepted Answer

Higher activation energy leads to a lower rate constant.

Answer

Higher activation energy results in a higher rate constant.

Answer

Activation energy has no impact on the rate constant.

Answer

The Arrhenius equation cannot determine the relationship between activation energy and rate constant.

Question 10

How does increasing the surface area of the reactants affect the reaction rate? Explain your answer using collision theory.

Accepted Answer

It increases the reaction rate by providing more active sites for collisions.

Answer

It has no effect.

Answer

It decreases the reaction rate by reducing the concentration of the reactants.

Answer

It affects only heterogeneous reactions, not homogeneous reactions.

Question 11

A reaction is first-order with respect to both A and B. What is the overall reaction order?

Accepted Answer

2

Answer

1

Answer

3

Answer

4

Question 12

If a reaction is first order with respect to reactant A and second order with respect to reactant B, what is the overall order of the reaction?

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 13

In a reaction between A and B, the rate law is determined to be Rate = k[A]^2[B]^1/2. What is the reaction order with respect to A and B, respectively?

Accepted Answer

Second order, half order

Answer

First order, second order

Answer

Half order, first order

Answer

First order, half order

Question 14

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

Accepted Answer

Presence of a catalyst

Answer

Concentration of reactants

Answer

Temperature

Answer

Surface area of reactants (for solids)

Question 15

A catalyst:

Accepted Answer

Decreases the activation energy of a reaction

Answer

Increases the activation energy of a reaction

Answer

Changes the order of a reaction

Answer

Is consumed in the reaction

Question 16

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

Accepted Answer

The concentration of reactants to decrease by 50%

Answer

The concentration of products to increase by 50%

Answer

The rate of reaction to decrease by 50%

Answer

The activation energy to decrease by 50%

Question 17

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

Accepted Answer

Volume of the reaction container

Answer

Temperature

Answer

Concentration of reactants

Answer

Presence of a catalyst

Question 18

Which characteristic is unique to a heterogeneous catalyst?

Accepted Answer

Exists in a different phase from the reactants

Answer

Increases the activation energy of the reaction

Answer

Decreases the rate of the reaction

Answer

Is consumed during the reaction

Question 19

Which technique is commonly used to study the kinetics of fast reactions?

Accepted Answer

Stopped-flow method

Answer

Gas chromatography

Answer

NMR spectroscopy

Answer

UV-Vis spectrophotometry

Question 20

In biological reactions, enzymes play the role of:

Accepted Answer

Lowering the activation energy of the reaction

Answer

Increasing the activation energy of the reaction

Answer

Providing an alternative pathway for the reaction

Answer

Consuming the products of the reaction

Question 21

The following reaction is exothermic: A + B ⇌ C + D. Which of the following changes in reaction conditions will shift the equilibrium to the right?

Accepted Answer

Increasing temperature

Answer

Decreasing temperature

Answer

Increasing pressure

Answer

Decreasing pressure

Question 22

Which of the following intermolecular forces is the weakest?

Accepted Answer

London dispersion forces

Answer

Dipole-dipole forces

Answer

Hydrogen bonding

Answer

Ion-dipole forces

Question 23

Determine the factor that does not influence the rate of a chemical reaction.

Accepted Answer

Volume of the container

Answer

Concentration of the reactants

Answer

Temperature

Answer

Nature of the reactants

Question 24

Explain how a catalyst influences the rate of a reaction.

Accepted Answer

Changes the activation energy of the reaction

Answer

Alters the products of the reaction

Answer

Changes the reactants of the reaction

Answer

Modifies the reaction mechanism

Question 25

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

Accepted Answer

Volume of the reaction vessel

Answer

Concentration of reactants

Answer

Temperature

Answer

Surface area

Question 26

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

Accepted Answer

The concentration of the reactant to decrease by half

Answer

The concentration of the product to double

Answer

The rate constant to double

Answer

The activation energy to halve

Question 27

Which reaction is an example of a unimolecular reaction?

Accepted Answer

2NO(g) → 2NO2(g)

Answer

NO(g) + O2(g) → NO2(g)

Answer

NO2(g) + NO2(g) → N2O4(g)

Answer

NO(g) + NO(g) + O2(g) → 2NO2(g)

Question 28

A catalyst:

Accepted Answer

Lowers the activation energy of a reaction

Answer

Increases the activation energy of a reaction

Answer

Changes the products of a reaction

Answer

Decreases the rate of a reaction

Question 29

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

Accepted Answer

The color of the reactants

Answer

The concentration of the reactants

Answer

The surface area of the solid reactants

Answer

The temperature of the reaction

Question 30

The rate law for a given chemical reaction is an equation that expresses the dependence of the reaction rate on the concentrations of the reactants. Which of the following is the rate law for a reaction that is second order with respect to reactant A and first order with respect to reactant B?

Accepted Answer

Rate = k[A]^2[B]

Answer

Rate = k[A]^2[B]^2

Answer

Rate = k[A]^3[B]

Answer

Rate = k[A][B]^2

Question 31

The half-life of a radioactive isotope is the time it takes for half of the atoms in a sample to decay. Which of the following is the correct relationship between the half-life (t1/2) and the fraction of the isotope remaining (N/N0) after time t?

Accepted Answer

N/N0 = (1/2)^(t/t1/2)

Answer

N/N0 = (1/2) * (t/t1/2)

Answer

N/N0 = 2^(t/t1/2)

Answer

N/N0 = 2 * (t/t1/2)

Question 32

The activation energy of a reaction is lowered by the presence of a catalyst. What is the effect of this on the rate of the reaction?

Accepted Answer

The rate of the reaction increases

Answer

The rate of the reaction remains the same

Answer

The rate of the reaction decreases

Answer

The activation energy of the reaction increases

Question 33

Which of the following is NOT a method for increasing the rate of a reaction?

Accepted Answer

Decreasing the temperature

Answer

Using a catalyst

Answer

Increasing the surface area of the reactants

Answer

Increasing the concentration of the reactants

Question 34

Homogeneous reactions are reactions in which all the reactants and products are in the same phase. Which of the following is an example of a homogeneous reaction?

Accepted Answer

The reaction of hydrogen and oxygen to form water

Answer

The reaction of carbon and oxygen to form carbon dioxide

Answer

The reaction of sodium and water to form sodium hydroxide and hydrogen

Question 35

The rate of a reaction is the change in concentration of the reactants or products over time. For a first-order reaction, the rate law is: Rate = k[A], where k is the rate constant and [A] is the concentration of the reactant. If the rate of a reaction is 1.0 x 10^-2 M/s when the concentration of the reactant is 0.5 M, determine the order of the reaction.

Accepted Answer

First order

Answer

Third order

Answer

Zero order

Answer

Second order

Question 36

In a first-order reaction, the half-life is solely dependent on the:

Accepted Answer

Rate constant

Answer

Temperature

Answer

Reaction order

Answer

Initial concentration

Question 37

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

Accepted Answer

Amount of product formed

Answer

Temperature

Answer

Surface area of reactants

Answer

Concentration of reactants

Question 38

For a reaction with the rate expression rate = k[A]^2[B], predict the change in the reaction rate if the concentration of A is doubled and the concentration of B is halved.

Accepted Answer

Unchanged

Answer

Decreased by a factor of 2

Answer

Increased by a factor of 2

Answer

Increased by a factor of 4

Question 39

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

Accepted Answer

H+

Answer

MnO2

Answer

Ni

Answer

Pd

Question 40

Consider the following reaction mechanism:
Step 1: A + B → C (slow)
Step 2: C + D → E (fast)
Determine the overall rate law for this reaction.

Accepted Answer

rate = k[A][B]

Answer

rate = k[C][D]

Answer

rate = k[A][B][C]

Answer

rate = k[A][B][D]

Question 41

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

Accepted Answer

The concentration of the products

Answer

The temperature

Answer

The concentration of the reactants

Answer

The surface area of the reactants

Question 42

The rate constant for a first-order reaction is 0.05 s^-1. What is the half-life of the reaction?

Accepted Answer

13.9 s

Answer

55.6 s

Answer

6.9 s

Answer

27.8 s

Question 43

A catalyst accelerates a reaction by:

Accepted Answer

Providing an alternative pathway with a lower activation energy

Answer

Decreasing the temperature of the reaction

Answer

Increasing the entropy of the reaction

Question 44

Which of the following is a homogeneous catalyst?

Accepted Answer

H+

Answer

Pt

Answer

Ni

Question 45

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

Accepted Answer

The rate is independent of the concentration of the reactants

Answer

The rate is inversely proportional to the concentration of the reactants

Answer

The rate is proportional to the concentration of the reactants

Question 46

A reaction is found to be first order with respect to reactant A and second order with respect to reactant B. What is the overall order of the reaction?

Accepted Answer

Third order

Answer

First order

Answer

Zero order

Answer

Second order

Question 47

The rate law for the reaction 2A + B → C is found to be rate = k[A][B]. What are the orders of the reaction with respect to A and B, respectively?

Accepted Answer

First order with respect to A and first order with respect to B

Answer

Zero order with respect to A and first order with respect to B

Answer

Second order with respect to A and first order with respect to B

Answer

First order with respect to A and second order with respect to B

Question 48

The rate constant for a first-order reaction is 0.05 s⁻¹. What is the half-life of the reaction?

Accepted Answer

13.9 s

Answer

20 s

Answer

10 s

Answer

5 s

Question 49

The following data were obtained for the reaction A → B: 
 [A] (mol/L) | Time (s) 
 1.00 | 0 
 0.50 | 10 
 0.25 | 20 
 What is the order of the reaction?

Accepted Answer

First order

Answer

Second order

Answer

Cannot be determined from the data provided

Answer

Zero order

Question 50

A catalyst speeds up a reaction by:

Accepted Answer

Lowering the activation energy

Answer

Changing the equilibrium constant

Answer

Increasing the temperature

Answer

Increasing the concentration of reactants