Energy Changes in Chemistry Quizzes: Test Your Understanding

Question 1

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

Accepted Answer

Enthalpy change of the reaction

Answer

Concentration of reactants

Answer

Temperature

Answer

Surface area of reactants

Question 2

The enthalpy change of a reaction is best described as:

Accepted Answer

The heat absorbed or released during the reaction

Answer

The change in entropy of the reaction

Answer

The activation energy required for the reaction

Answer

The spontaneity of the reaction

Question 3

The Gibbs free energy change (ΔG) of a reaction represents:

Accepted Answer

The maximum work that can be obtained from the reaction

Answer

The difference in internal energy between products and reactants

Answer

The change in entropy of the system

Answer

The activation energy required for the reaction

Question 4

Which of the following reactions releases heat?

Accepted Answer

Combustion of methane

Answer

Photosynthesis

Answer

Melting of ice

Answer

Dissolution of potassium chloride in water

Question 5

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

Accepted Answer

Is consumed in the reaction

Answer

Increases the rate of a reaction

Answer

Lowers the activation energy of the reaction

Answer

Is present in the same amount at the end of the reaction as at the beginning

Question 6

The enthalpy change of combustion refers to:

Accepted Answer

The heat released when a substance reacts with oxygen

Answer

The heat absorbed when a substance reacts with oxygen

Answer

The change in entropy of the reaction

Answer

The activation energy required for the combustion reaction

Question 7

What is the standard enthalpy change of formation of water?

Accepted Answer

-286 kJ/mol (correct answer)

Answer

0 kJ/mol

Answer

286 kJ/mol

Answer

572 kJ/mol

Question 8

Which of the following is an exothermic reaction?

Accepted Answer

Burning of methane (correct answer)

Answer

Dissolution of sodium hydroxide in water

Answer

Melting of ice

Answer

Photosynthesis

Question 9

What is the relationship between entropy and randomness?

Accepted Answer

Entropy increases as randomness increases (correct answer)

Answer

Entropy decreases as randomness increases

Answer

Entropy is not related to randomness

Answer

Randomness increases as entropy decreases

Question 10

What is the relationship between enthalpy and entropy in a spontaneous reaction?

Accepted Answer

Enthalpy must be negative and entropy must be positive (correct answer)

Answer

Enthalpy must be positive and entropy must be negative

Answer

Enthalpy and entropy can be either positive or negative

Answer

Enthalpy and entropy must both be zero

Question 11

What is the equilibrium constant for a reaction?

Accepted Answer

The ratio of the concentrations of products to reactants at equilibrium (correct answer)

Answer

The ratio of the concentrations of reactants to products at equilibrium

Answer

The value of the activation energy for the forward reaction

Answer

The value of the activation energy for the reverse reaction

Question 12

Which of the following is a catalyst?

Accepted Answer

A substance that speeds up a reaction without being consumed (correct answer)

Answer

A substance that slows down a reaction

Answer

A substance that is produced as a product of a reaction

Answer

A substance that is consumed as a reactant in a reaction

Question 13

The SI unit of energy is the:

Accepted Answer

Joule

Answer

Kelvin

Answer

Mole

Answer

Watt

Question 14

A chemical reaction with a negative enthalpy change is:

Accepted Answer

Exothermic

Answer

Endothermic

Answer

Spontaneous

Answer

Non-spontaneous

Question 15

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

Accepted Answer

Particle size of reactants

Answer

Temperature

Answer

Concentration of reactants

Answer

Presence of a catalyst

Question 16

Which of the following is an example of an exothermic reaction?

Accepted Answer

Combustion of methane

Answer

Dissolution of sodium chloride in water

Answer

Respiration

Answer

Melting of ice

Question 17

Entropy is a measure of the:

Accepted Answer

Disorderliness of a system

Answer

Orderliness of a system

Answer

Temperature of a system

Answer

Energy of a system

Question 18

A catalyst in a chemical reaction is a substance that:

Accepted Answer

Speeds up the reaction without being consumed

Answer

Slows down the reaction

Answer

Is a product of the reaction

Answer

Is a reactant in the reaction

Question 19

A reaction with a positive entropy change is considered to be:

Accepted Answer

Spontaneous

Answer

Non-spontaneous

Answer

Endothermic

Answer

Exothermic

Question 20

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

Accepted Answer

Addition of a catalyst

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Volume (for gas reactions)

Question 21

The activation energy of a reaction is the:

Accepted Answer

Minimum energy required for a reaction to occur

Answer

Maximum energy released during a reaction

Answer

Energy difference between the reactants and products

Answer

Rate constant for the reaction

Question 22

Identify the process that illustrates an exothermic reaction:

Accepted Answer

Burning wood

Answer

Dissolving salt into water

Answer

Neutralizing an acid with a base

Answer

Evaporation of water

Question 23

Which unit is used to measure energy in chemistry?

Accepted Answer

Joules

Answer

Calories

Answer

Watts

Answer

Electronvolts

Question 24

What is the role of a catalyst?

Accepted Answer

A substance that increases the reaction rate without being consumed

Answer

A reactant that is consumed during the reaction

Answer

A product formed at the end of the reaction

Answer

A substance that slows down the reaction rate

Question 25

Describe the activation energy of a reaction.

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The energy released by the reaction

Answer

The difference in energy between reactants and products

Answer

The rate of the reaction

Question 26

Identify an endothermic reaction:

Accepted Answer

Dissolving sodium chloride in water

Answer

Burning methane

Answer

Neutralizing hydrochloric acid with sodium hydroxide

Answer

Condensation of water vapor

Question 27

Explain the effect of increasing temperature on the equilibrium constant of an exothermic reaction.

Accepted Answer

The equilibrium constant decreases

Answer

The equilibrium constant increases

Answer

The equilibrium constant remains unchanged

Answer

The equilibrium constant becomes negative

Question 28

Which of the following describes the enthalpy change for an exothermic reaction?

Accepted Answer

Negative

Answer

Positive

Answer

Zero

Question 29

How is entropy related to randomness in a system?

Accepted Answer

Entropy is directly proportional to randomness.

Answer

Entropy is inversely proportional to randomness.

Answer

Entropy is not related to randomness.

Question 30

Which of the following processes is considered spontaneous?

Accepted Answer

A reaction with a negative Gibbs free energy change

Answer

A reaction with a positive Gibbs free energy change

Answer

A reaction that requires activation energy

Question 31

Which of the following definitions best describes activation energy?

Accepted Answer

The minimum amount of energy required for a reaction to occur.

Answer

The maximum amount of energy released by a reaction.

Answer

The difference between the enthalpy change and the Gibbs free energy change.

Question 32

The enthalpy change of a reaction is negative. What does this indicate?

Accepted Answer

The reaction releases heat (exothermic)

Answer

The reaction absorbs heat (endothermic)

Answer

The reaction is spontaneous

Answer

The reaction is non-spontaneous

Question 33

What is the SI unit of entropy?

Accepted Answer

Joules per kelvin

Answer

Joules

Answer

Kelvins

Answer

Moles per kilogram

Question 34

What is the relationship between free energy change (ΔG) and the spontaneity of a reaction?

Accepted Answer

A negative ΔG indicates a spontaneous reaction

Answer

A positive ΔG indicates a spontaneous reaction

Answer

ΔG is not related to spontaneity

Answer

A zero ΔG indicates a spontaneous reaction

Question 35

What is the activation energy of a reaction?

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The maximum energy released in a reaction

Answer

The change in entropy of a reaction

Answer

The change in free energy of a reaction

Question 36

What is the role of entropy in chemical reactions?

Accepted Answer

To determine the spontaneity of a reaction

Answer

To calculate the activation energy of a reaction

Answer

To predict the rate of a reaction

Answer

To measure the enthalpy change of a reaction

Question 37

Which of the following is a measure of the randomness or disorder of a system?

Accepted Answer

Entropy

Answer

Enthalpy

Answer

Free energy

Answer

Activation energy

Question 38

The unit of entropy is:

Accepted Answer

Joules per mole per Kelvin

Answer

Joules per Kelvin

Answer

Kelvin per mole

Answer

Moles per liter

Question 39

A spontaneous reaction has a:

Accepted Answer

Negative ΔG

Answer

Positive ΔG

Answer

ΔG of zero

Answer

ΔG that depends on temperature

Question 40

When products have more energy than reactants, the enthalpy change of the reaction is:

Accepted Answer

Positive

Answer

Negative

Answer

Zero

Answer

Cannot be determined from the given information

Question 41

Which property measures the randomness or disorder of a system?

Accepted Answer

Entropy

Answer

Enthalpy

Answer

Gibbs free energy

Answer

Activation energy

Question 42

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

Accepted Answer

Decreases it

Answer

Increases it

Answer

Has no effect

Answer

Reverses it

Question 43

An example of a redox reaction is:

Accepted Answer

Combustion of methane

Answer

Neutralization of an acid and a base

Answer

Precipitation of a salt

Answer

Dissolution of sugar in water

Question 44

The relationship between ΔG and the equilibrium constant (Keq) is given by:

Accepted Answer

ΔG = -RTlnKeq

Answer

ΔG = RTlnKeq

Answer

ΔG = KeqRT

Answer

ΔG = -KeqRT

Question 45

What is the correct unit of enthalpy change?

Accepted Answer

Kilojoules per mole (kJ mol^-1)

Answer

Joules per mole (J mol^-1)

Answer

Joules (J)

Answer

Kilojoules (kJ)

Question 46

In an exothermic reaction, what is the sign of the enthalpy change?

Accepted Answer

Negative

Answer

Positive

Answer

Zero

Answer

Varies depending on the reaction

Question 47

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

Accepted Answer

Type of products

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 48

What is the relationship between free energy change and the difference in enthalpy and entropy?

Accepted Answer

Free energy change equals enthalpy change minus entropy change multiplied by temperature.

Answer

Free energy change equals enthalpy change plus entropy change multiplied by temperature.

Answer

Free energy change equals entropy change minus enthalpy change multiplied by temperature.

Answer

Free energy change equals enthalpy change multiplied by entropy change.

Question 49

Which of the following processes is spontaneous?

Accepted Answer

A process with a negative free energy change

Answer

A process with a positive free energy change

Answer

A process with no entropy change

Answer

A process at equilibrium

Question 50

What is the activation energy of a reaction?

Accepted Answer

The minimum amount of energy required for a reaction to occur

Answer

The energy released during a reaction

Answer

The energy absorbed during a reaction

Answer

The maximum amount of energy possible in a reaction

Question 51

What is entropy change?

Accepted Answer

The change in randomness or disorder of a system

Answer

The change in energy of a system

Answer

The change in temperature of a system

Answer

The change in volume of a system

Question 52

What 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

Answer

A substance that is consumed in a reaction

Answer

A substance that alters the products of a reaction

Question 53

What is the relationship between enthalpy change and spontaneity?

Accepted Answer

Spontaneity depends on both enthalpy change and entropy change

Answer

Exothermic reactions are always spontaneous

Answer

Endothermic reactions are always spontaneous

Answer

Exothermic reactions are sometimes spontaneous

Question 54

Which of the following techniques can be used to measure the enthalpy change of a reaction?

Accepted Answer

Bomb calorimetry

Answer

Titration

Answer

Spectroscopy

Answer

Chromatography

Question 55

What is the activation energy of a reaction?

Accepted Answer

The minimum amount of energy required for a reaction to occur

Answer

The maximum amount of energy released in a reaction

Answer

The difference between the energies of the reactants and products

Answer

The rate at which a reaction proceeds

Question 56

Which of the following processes is an example of an exothermic reaction?

Accepted Answer

Combustion of methane

Answer

Melting of ice

Answer

Evaporation of water

Answer

Dissolving salt in water

Question 57

Which of the following factors does NOT affect 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 58

What does the activation energy of a chemical reaction represent?

Accepted Answer

The minimum energy required for the reaction to occur

Answer

The maximum energy released by the reaction

Answer

The difference in energy between reactants and products

Answer

The rate at which the reaction proceeds

Question 59

Which of the following reactions has a negative change in free energy?

Accepted Answer

Photosynthesis

Answer

Rusting of iron

Answer

Melting of ice

Answer

Evaporation of water

Question 60

What is the entropy change associated with the melting of a solid?

Accepted Answer

Positive

Answer

Negative

Answer

Zero

Answer

Dependent on the substance

Question 61

Which of the following reactions is a combustion reaction?

Accepted Answer

Reaction of magnesium with oxygen

Answer

Neutralization of an acid with a base

Answer

Decomposition of hydrogen peroxide

Answer

Displacement of copper from copper sulfate by iron

Question 62

Which of the following is an example of a catalyst?

Accepted Answer

Enzymes

Answer

Water

Answer

Sodium chloride

Answer

Carbon dioxide

Question 63

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

Accepted Answer

Increases the rate

Answer

Decreases the rate

Answer

No effect on the rate

Answer

Dependent on the specific reaction

Question 64

At equilibrium, what is the value of the free energy change (ΔG) of a reaction?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Infinity