Chemical Thermodynamics Quizzes: Master the Fundamentals

Question 1

What expression represents the standard free energy change of a reaction under constant temperature and pressure?

Accepted Answer

-RTln(K)

Answer

+RTln(K)

Answer

ΔH - TΔS

Answer

ΔH - RTln(Q)

Question 2

What is the significance of Gibbs free energy in chemical reactions?

Accepted Answer

It represents the maximum non-expansion work obtainable from a reaction at constant temperature and pressure.

Answer

It is always negative for spontaneous reactions.

Answer

It only accounts for enthalpy changes in a reaction.

Answer

It is not useful in determining the equilibrium state of a reaction.

Question 3

What does a negative Gibbs free energy (ΔG) indicate about the spontaneity of a chemical reaction?

Accepted Answer

The reaction is spontaneous and will proceed in the forward direction without an external energy input.

Answer

The reaction is non-spontaneous and requires an external energy input to proceed.

Answer

The reaction is at equilibrium and the concentrations of reactants and products do not change.

Answer

The reaction is spontaneous and requires an external energy input to proceed.

Question 4

For the chemical reaction A + B → C + D, which thermodynamic property determines if the reaction is spontaneous under specific conditions?

Accepted Answer

Free energy change

Answer

Enthalpy change

Answer

Entropy change

Answer

Equilibrium constant

Question 5

For the chemical reaction A + B <=> C + D, which expression represents the equilibrium constant (K)?

Accepted Answer

K = [A][B]/[C][D]

Answer

K = [C][D]/[A][B]

Answer

K = [A] + [B] - [C] - [D]

Answer

K = 1/([A][B]/[C][D])

Question 6

For the chemical reaction at equilibrium:

A + B <=> C + D

Which statement accurately describes the equilibrium constant, K, for this reaction?

Accepted Answer

K equals the ratio of product concentrations to reactant concentrations at equilibrium.

Answer

K is always greater than 1, indicating that products are favored at equilibrium.

Answer

K is always less than 1, indicating that reactants are favored at equilibrium.

Answer

K is unaffected by temperature or pressure.

Question 7

Which of the following describes the Gibbs free energy change for exothermic reactions?

Accepted Answer

Always negative

Answer

Always positive

Answer

Equal to the enthalpy change

Answer

Independent of temperature

Question 8

Which factor does NOT affect the equilibrium constant (K) of a chemical reaction?

Accepted Answer

Surface area of the catalyst

Answer

Reactant concentration

Answer

Product concentration

Answer

Temperature

Question 9

In chemical thermodynamics, which of the following indicates that a reaction will occur spontaneously?

Accepted Answer

A reaction with an equilibrium constant greater than 1

Answer

A reaction with a positive Gibbs free energy change

Answer

A reaction with a negative change in entropy

Answer

A reaction with an equilibrium constant less than 1

Question 10

In a spontaneous chemical reaction at constant temperature and pressure, what is the characteristic of the change in Gibbs free energy (ΔG)?

Accepted Answer

ΔG is negative

Answer

ΔG is positive

Answer

ΔG is zero

Answer

ΔG cannot be determined

Question 11

In chemical thermodynamics, which factor has **no direct** impact on the spontaneity of a reaction?

Accepted Answer

Reaction rate

Answer

Enthalpy change

Answer

Entropy change

Answer

Temperature

Question 12

For the chemical reaction at equilibrium: aA + bB <=> cC + dD, which expression represents the equilibrium constant (K)?

Accepted Answer

K = ([C]^c[D]^d)/([A]^a[B]^b)

Answer

K = (a[A] - b[B])/(c[C] + d[D])

Answer

K = (a+b)/(c+d)

Answer

K = [A][B]/[C][D]

Question 13

In an exothermic reaction, what happens to the enthalpy of the system?

Accepted Answer

Decreases

Answer

Increases

Answer

Stays the same

Question 14

Which of the following equations represents the equilibrium constant (Kc) for the reaction: aA + bB <=> cC + dD?

Accepted Answer

Kc = [A]^a[B]^b/[C]^c[D]^d

Answer

Kc = [C]^c[D]^d/[A]^a[B]^b

Answer

Kc = [A]^a[B]^b + [C]^c[D]^d

Answer

Kc = [A]^a + [B]^b

Question 15

How does temperature influence the spontaneity of a chemical reaction? Consider the interplay between enthalpy and entropy changes.

Accepted Answer

The spontaneity of a reaction depends on the combined effect of enthalpy and entropy changes, and temperature can alter their balance.

Answer

Temperature has no impact on reaction spontaneity.

Answer

Reactions with negative enthalpy changes are always spontaneous, regardless of temperature.

Answer

Reactions with positive entropy changes are always spontaneous, regardless of temperature.

Question 16

Which of the following accurately describes the standard enthalpy of formation?

Accepted Answer

Enthalpy change when one mole of a compound is formed from its constituent elements in their standard states

Answer

Enthalpy change when one gram of a compound is formed from its constituent elements in their standard states

Answer

Enthalpy change when one mole of a compound is formed from its constituent elements in their non-standard states

Answer

Enthalpy change when one gram of a compound is formed from its constituent elements in their non-standard states

Question 17

For a reaction with an equilibrium constant of 0.5, what is the sign of the standard free energy change (ΔG°)?

Accepted Answer

Negative

Answer

Positive

Answer

Zero

Answer

Cannot be determined

Question 18

Which factor does NOT influence the equilibrium constant of a reaction?

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Presence of a catalyst

Question 19

Which of the following processes is spontaneous?

Accepted Answer

A reaction with a negative ΔG°

Answer

A reaction with a positive ΔG°

Answer

A reaction with a ΔG° = 0

Answer

A reaction with a ΔH° < 0

Question 20

Entropy change of a system can be defined as:

Accepted Answer

A measure of the disorder or randomness of the system

Answer

A measure of the energy of the system

Answer

A measure of the temperature of the system

Answer

A measure of the volume of the system

Question 21

The Gibbs free energy of a system is represented by:

Accepted Answer

G = H - TS

Answer

G = H + TS

Answer

G = T - HS

Answer

G = TS - H

Question 22

Which condition represents a system at equilibrium?

Accepted Answer

dG = 0

Answer

dH = 0

Answer

dS = 0

Answer

dV = 0

Question 23

The enthalpy change for a reaction is defined as:

Accepted Answer

The difference between the enthalpy of the products and the reactants

Answer

The sum of the enthalpy of the products and the reactants

Answer

The change in entropy multiplied by the temperature

Answer

The change in volume multiplied by the pressure

Question 24

The Gibbs free energy change for a reaction is:

Accepted Answer

The difference between the enthalpy change and the entropy change multiplied by the temperature

Answer

The difference between the entropy change and the enthalpy change multiplied by the temperature

Answer

The sum of the enthalpy change and the entropy change multiplied by the temperature

Answer

Equal to the equilibrium constant multiplied by the temperature

Question 25

A spontaneous reaction is characterized by:

Accepted Answer

A negative change in Gibbs free energy

Answer

A positive change in Gibbs free energy

Answer

An increase in enthalpy

Answer

A decrease in entropy

Question 26

The standard enthalpy change for a reaction is:

Accepted Answer

The enthalpy change under standard conditions (298 K and 1 atm)

Answer

The enthalpy change for a non-standard reaction

Answer

The enthalpy change in the presence of a catalyst

Answer

The enthalpy change for a reaction at 0 K

Question 27

The second law of thermodynamics implies that:

Accepted Answer

The total entropy of the universe never decreases

Answer

The total energy of the universe always increases

Answer

Spontaneous reactions are always endothermic

Answer

Heat always flows from cold to hot objects

Question 28

A catalyst:

Accepted Answer

Increases the rate of reaction by providing an alternative pathway with lower activation energy

Answer

Changes the equilibrium constant of the reaction

Answer

Provides heat for the reaction

Answer

Decreases the entropy change of the reaction

Question 29

When is the Gibbs free energy change of a reaction negative?

Accepted Answer

When the reaction is spontaneous

Answer

When the reaction is non-spontaneous

Answer

When the reaction is at equilibrium

Answer

When the entropy of the system increases

Question 30

What is the standard enthalpy of formation of an element in its most stable form?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Cannot be determined

Question 31

Which process would be considered exothermic?

Accepted Answer

Combustion of methane

Answer

Condensation of water

Answer

Melting of ice

Answer

Evaporation of water

Question 32

Which process is considered reversible?

Accepted Answer

Expansion of an ideal gas against a vacuum

Answer

Combustion of a fuel

Answer

Melting of ice at 0°C

Answer

Transfer of heat through a conductor

Question 33

In the equilibrium reaction A(g) + B(g) <=> 2C(g) + heat, how does increasing the temperature affect the equilibrium constant, K?

Accepted Answer

K increases, favoring the forward reaction.

Answer

K decreases, favoring the backward reaction.

Answer

K remains constant, and the reaction is unaffected by temperature.

Answer

The relationship between K and temperature depends on the initial molar ratio of A to B.

Question 34

Which of the following is NOT a characteristic of a system in thermodynamic equilibrium?

Accepted Answer

Continuous exchange of energy or matter with the surroundings

Answer

Constant temperature

Answer

Constant pressure

Answer

Constant volume

Question 35

The enthalpy of reaction (ΔH) represents:

Accepted Answer

Heat absorbed or released by the reaction at constant pressure

Answer

Change in internal energy of the system

Answer

Work done by the system

Answer

Entropy change of the system

Question 36

Which of the following factors does NOT influence the equilibrium constant of a reaction?

Accepted Answer

Volume of the container

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants and products

Question 37

The standard enthalpy of formation for an element in its most stable form is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Temperature-dependent

Question 38

Identify the spontaneous process:

Accepted Answer

Ice melting at room temperature

Answer

Water flowing uphill

Answer

A chemical reaction with ΔG > 0

Answer

A reaction with constant entropy (ΔS = 0)

Question 39

The heat capacity of a substance represents:

Accepted Answer

Heat required to raise the temperature of one mole of the substance by one degree Celsius

Answer

Heat required to raise the temperature of one gram of the substance by one degree Celsius

Answer

Heat released when one mole of the substance undergoes a chemical reaction

Answer

Heat absorbed when one gram of the substance undergoes a phase change

Question 40

Which of the following is a closed system?

Accepted Answer

A sealed container filled with gas

Answer

A cylinder with a movable piston

Answer

A beaker of water exposed to the atmosphere

Answer

A balloon filled with air

Question 41

Entropy of a system:

Accepted Answer

Measures the disorder or randomness of the system

Answer

Is always positive for spontaneous processes

Answer

Is always negative for non-spontaneous processes

Answer

Is independent of the system's temperature

Question 42

Which of the following is NOT a fundamental thermodynamic property?

Accepted Answer

Volume

Answer

Temperature

Answer

Pressure

Answer

Entropy

Question 43

The equilibrium constant (K) for a reaction is:

Accepted Answer

A constant that determines the extent of the reaction at equilibrium

Answer

A constant that determines the direction of the reaction

Answer

A constant that determines the rate of the reaction

Answer

A constant that determines the activation energy of the reaction

Question 44

In an isothermal process, which parameter remains constant?

Accepted Answer

Temperature

Answer

Pressure

Answer

Volume

Answer

Enthalpy

Question 45

Entropy is a measure of:

Accepted Answer

Disorder or randomness

Answer

Energy

Answer

Temperature

Answer

Pressure

Question 46

Which of the following is **not** a system type in chemical thermodynamics?

Accepted Answer

A burning candle

Answer

Closed system

Answer

Open system

Answer

A sealed container of gas

Question 47

Which term describes the heat transfer **at constant volume**?

Accepted Answer

Enthalpy

Answer

Entropy

Answer

Internal energy

Answer

Free energy

Question 48

The equilibrium constant (K) of a chemical reaction is:

Accepted Answer

The ratio of products to reactants at equilibrium

Answer

The rate constant for the forward reaction

Answer

The change in Gibbs free energy

Answer

The temperature at which the reaction occurs

Question 49

The standard enthalpy change (ΔH°) of a reaction is:

Accepted Answer

The enthalpy change when the reactants and products are in their standard states

Answer

The enthalpy change when the reactants and products are at 298 K

Answer

The enthalpy change when the reaction occurs at constant temperature

Answer

The enthalpy change when the reaction occurs at constant volume

Question 50

The Van der Waals equation of state accounts for:

Accepted Answer

Both of the above

Answer

The finite volume of the molecules

Answer

The interactions between the molecules

Answer

Neither of the above

Question 51

How does an increase in temperature affect the equilibrium constant (Kc) for an exothermic reaction?

Accepted Answer

Kc decreases.

Answer

Kc increases.

Answer

Kc remains unchanged.

Answer

Kc reverses its sign.

Question 52

Which law states that the entropy of an isolated system always increases?

Accepted Answer

Second law of thermodynamics

Answer

First law of thermodynamics

Answer

Third law of thermodynamics

Answer

Zeroth law of thermodynamics

Question 53

According to the third law of thermodynamics, what is the entropy of a perfect crystal at absolute zero?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Undefined

Question 54

Express the Gibbs free energy (G) in terms of enthalpy (H), temperature (T), and entropy (S):

Accepted Answer

G = H - TS

Answer

G = U + TS

Answer

G = H + TS

Answer

G = U - TS

Question 55

Which thermodynamic property describes a system's resistance to change in its temperature?

Accepted Answer

Heat capacity

Answer

Internal energy

Answer

Entropy

Answer

Pressure

Question 56

A reaction has an equilibrium constant of 10. What is the ratio of products to reactants at equilibrium?

Accepted Answer

10:1

Answer

1:1

Answer

1:10

Answer

100:1

Question 57

Which of the following factors does NOT affect the enthalpy of a reaction?

Accepted Answer

Volume

Answer

Temperature

Answer

Pressure

Answer

Phase

Question 58

A closed system undergoes a reversible isothermal expansion. Which of the following statements is true?

Accepted Answer

Entropy remains constant

Answer

Entropy increases

Answer

Entropy decreases

Answer

Work is done on the system

Question 59

A gas undergoes an adiabatic expansion. What happens to its temperature?

Accepted Answer

Decreases

Answer

Increases

Answer

Remains constant

Answer

Depends on the specific gas

Question 60

What is the partial pressure of nitrogen in a mixture of gases with a total pressure of 1 atm and a mole fraction of nitrogen of 0.6?

Accepted Answer

0.6 atm

Answer

0.2 atm

Answer

0.4 atm

Answer

0.8 atm

Question 61

Establish the sign convention for enthalpy.

Accepted Answer

Positive for exothermic and negative for endothermic reactions

Answer

Negative for exothermic and positive for endothermic reactions

Answer

Positive for both exothermic and endothermic reactions

Answer

Negative for both exothermic and endothermic reactions

Question 62

Which of the following is the standard enthalpy change for a reaction?

Accepted Answer

Enthalpy of products - Enthalpy of reactants

Answer

Enthalpy of products + Enthalpy of reactants

Answer

Enthalpy of reaction divided by the temperature

Answer

Enthalpy of reactants - Enthalpy of products

Question 63

A reaction is exothermic if:

Accepted Answer

Heat is released

Answer

Heat is absorbed

Answer

Volume increases

Answer

Entropy decreases

Question 64

The equilibrium constant for a reaction is defined as the:

Accepted Answer

Ratio of the concentrations of products to reactants at equilibrium

Answer

Rate of the forward reaction divided by the rate of the reverse reaction

Answer

Change in enthalpy of the reaction