Energetics and Equilibrium Quizzes - Test Your Chemistry Knowledge

Question 1

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

Accepted Answer

Volume of the reaction vessel (assuming no gases are present)

Answer

Pressure (if gases are present)

Answer

Concentration of reactants

Answer

Concentration of products

Question 2

In a chemical reaction, which combination of enthalpy change (ΔH) and entropy change (ΔS) indicates that the reaction is both spontaneous and releases heat?

Accepted Answer

ΔH < 0, ΔS > 0

Answer

ΔH > 0, ΔS > 0

Answer

ΔH < 0, ΔS < 0

Answer

ΔH > 0, ΔS < 0

Question 3

The standard enthalpy change of formation of glucose is -1273 kJ/mol. This means that:

Accepted Answer

1 mol of glucose releases 1273 kJ of heat when formed from its elements.

Answer

1 mol of glucose absorbs 1273 kJ of heat when formed from its elements.

Answer

1 mol of glucose has an internal energy of -1273 kJ.

Answer

1 mol of glucose has an enthalpy of -1273 kJ.

Question 4

The equilibrium constant for a reaction is 4. What does this indicate?

Accepted Answer

The reaction will favor the formation of products at equilibrium.

Answer

The reaction will proceed until 4 moles of products are formed for every 1 mole of reactants.

Answer

The concentration of products will be four times greater than the concentration of reactants at equilibrium.

Answer

The reaction is irreversible.

Question 5

Define the free energy change of a reaction.

Accepted Answer

The difference between the enthalpy change and the entropy change of the reaction.

Answer

The maximum amount of work that can be done by the reaction.

Answer

The difference between the potential energy of the reactants and products.

Answer

The change in internal energy of the system.

Question 6

Entropy is a measure of:

Accepted Answer

Disorder

Answer

Order

Answer

Energy

Answer

Temperature

Question 7

The standard enthalpy of formation of an element in its standard state is defined as:

Accepted Answer

0 kJ mol^-1

Answer

1 kJ mol^-1

Answer

10 kJ mol^-1

Answer

100 kJ mol^-1

Question 8

Under standard state conditions, the enthalpy change of a reaction is defined as the enthalpy change when reactants and products are at:

Accepted Answer

1 atm and 298 K

Answer

1 atm and 0 K

Answer

1 mol and 0 K

Answer

1 mol and 298 K

Question 9

The spontaneity of a reaction depends on the:

Accepted Answer

Enthalpy and entropy changes

Answer

Enthalpy change only

Answer

Entropy change only

Answer

Temperature only

Question 10

According to Le Chatelier's principle, adding more product to an equilibrium reaction will:

Accepted Answer

Shift the equilibrium to the product side

Answer

Shift the equilibrium to the reactant side

Answer

Have no effect on the equilibrium position

Answer

Increase the rate of the forward reaction

Question 11

The standard free energy change (ΔG°) for a reaction at equilibrium is:

Accepted Answer

Always zero

Answer

Always positive

Answer

Always negative

Answer

Cannot be determined without additional information

Question 12

Which process involves a decrease in entropy?

Accepted Answer

Condensation of water vapor

Answer

Melting of ice

Answer

Sublimation of dry ice

Answer

Dissolution of salt in water

Question 13

What is the standard enthalpy of formation of water?

Accepted Answer

-285.8 kJ/mol

Answer

0 kJ/mol

Answer

285.8 kJ/mol

Answer

571.6 kJ/mol

Question 14

Which reaction has the highest activation energy?

Accepted Answer

2N2O5(g) → 4NO2(g) + O2(g)

Answer

CH3CH2Br(l) + NaOH(aq) → CH3CH2OH(l) + NaBr(aq)

Answer

2H2(g) + O2(g) → 2H2O(g)

Answer

CO(g) + 2H2(g) → CH3OH(g)

Question 15

For an exothermic reaction, the enthalpy change is:

Accepted Answer

Negative

Answer

Positive

Answer

Zero

Answer

Always positive

Question 16

Which of the following is the unit of entropy?

Accepted Answer

Joules per mole Kelvin

Answer

Joules

Answer

Joules per mole

Answer

Kelvins

Question 17

The equilibrium constant for a reaction is:

Accepted Answer

The ratio of products to reactants at equilibrium

Answer

The ratio of reactants to products at equilibrium

Answer

The change in free energy of the reaction

Answer

The activation energy of the reaction

Question 18

The Gibbs free energy change for a reaction is:

Accepted Answer

The difference between the enthalpy and temperature-entropy product changes

Answer

The difference between the entropy and enthalpy changes

Answer

The sum of the enthalpy and entropy changes

Answer

The product of the enthalpy and entropy changes

Question 19

Which of the following is NOT a condition for chemical equilibrium?

Accepted Answer

External influence

Answer

No net change in concentrations of reactants and products

Answer

Constant temperature

Answer

The forward and reverse reactions occur at the same rate

Question 20

The activation energy of a reaction is:

Accepted Answer

The minimum energy required for a reaction to occur

Answer

The maximum energy released by a reaction

Answer

The energy difference between reactants and products

Answer

The rate of a reaction

Question 21

Define the standard enthalpy change of formation of a substance in its standard state.

Accepted Answer

The enthalpy change when 1 mol of the substance is formed from its constituent elements under standard conditions of temperature and pressure (298 K and 1 bar).

Answer

The enthalpy change when 1 g of the substance is formed from its constituent elements.

Question 22

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

Accepted Answer

Entropy

Answer

Gibbs free energy

Answer

Enthalpy

Answer

Free energy

Question 23

Which reaction has the largest equilibrium constant?

Accepted Answer

A reaction with a large negative ΔG°

Answer

A reaction with a small negative ΔG°

Answer

A reaction with a large positive ΔG°

Answer

A reaction with a small positive ΔG°

Question 24

Define the standard free energy change of a reaction.

Accepted Answer

The change in free energy when 1 mol of the reactants are converted to 1 mol of the products under standard conditions of temperature and pressure (298 K and 1 bar).

Answer

The change in free energy when 1 g of the reactants are converted to 1 g of the products

Question 25

What is the defining characteristic of a spontaneous process?

Accepted Answer

A negative change in free energy (ΔG < 0)

Answer

A zero change in free energy (ΔG = 0)

Answer

A negative change in enthalpy (ΔH < 0)

Answer

A positive change in free energy (ΔG > 0)

Question 26

What is the unit for measuring entropy?

Accepted Answer

Joules per kelvin (J/K)

Answer

Kilojoules per mole (kJ/mol)

Answer

Kilojoules per kelvin (kJ/K)

Answer

Joules per mole (J/mol)

Question 27

Which of the following processes releases heat into the surroundings?

Accepted Answer

Combustion

Answer

Vaporization

Answer

Melting

Answer

Sublimation

Question 28

The entropy change for the reaction 2NO(g) + O2(g) → 2NO2(g) is negative. What does this tell us about the products and reactants?

Accepted Answer

The products are more ordered than the reactants.

Answer

The reaction is exothermic.

Answer

The reactants are more ordered than the products.

Answer

The reaction is endothermic.

Question 29

A positive standard Gibbs free energy change (ΔG°) for a reaction indicates that:

Accepted Answer

The reaction is non-spontaneous under standard conditions.

Answer

The reaction is spontaneous under standard conditions.

Answer

The reaction is at equilibrium under standard conditions.

Answer

The reactants are more stable than the products.

Question 30

Which reaction has the largest equilibrium constant (K) based on the provided standard Gibbs free energy changes (ΔG°)?

Accepted Answer

A + B → C (ΔG° = -20 kJ/mol)

Answer

G + H → I (ΔG° = -15 kJ/mol)

Answer

D + E → F (ΔG° = -5 kJ/mol)

Answer

J + K → L (ΔG° = -10 kJ/mol)

Question 31

The activation energy for the forward reaction in an equilibrium is 10 kJ/mol, and the activation energy for the reverse reaction is 20 kJ/mol. What is the overall activation energy difference between the forward and reverse reactions?

Accepted Answer

10 kJ/mol

Answer

30 kJ/mol

Answer

20 kJ/mol

Answer

0 kJ/mol

Question 32

The equilibrium constant (K) for a reaction is 10. What is the approximate value of ΔG° for the reaction at 298 K?

Accepted Answer

-5.7 kJ/mol

Answer

-20 kJ/mol

Answer

-10 kJ/mol

Answer

-15 kJ/mol

Question 33

Which of the following statements is TRUE about the enthalpy change (ΔH) for an exothermic reaction?

Accepted Answer

ΔH < 0

Answer

ΔH = 0

Answer

ΔH > 0

Answer

ΔH is unpredictable

Question 34

Which of the following processes is exothermic?

Accepted Answer

Condensation

Answer

Evaporation

Answer

Melting

Answer

Sublimation

Question 35

The equilibrium constant for the reaction A + B ⇌ C is 4. What is the value of Kc for the reverse reaction C ⇌ A + B?

Accepted Answer

0.25

Answer

4

Answer

2

Answer

16

Question 36

A reaction has a ΔH° of -20 kJ mol-1 and a ΔS° of +50 J mol-1 K-1. At what temperature will the reaction become spontaneous?

Accepted Answer

400 K

Answer

600 K

Answer

200 K

Answer

800 K

Question 37

What is the standard enthalpy change of combustion of methane (CH4) if the standard enthalpy of formation of CO2(g) and H2O(l) are -393.5 kJ mol-1 and -285.8 kJ mol-1, respectively?

Accepted Answer

-890.4 kJ mol-1

Answer

-787.1 kJ mol-1

Answer

-694.2 kJ mol-1

Answer

-993.7 kJ mol-1