Thermodynamics for Mechanical Engineers: Online Learning Quizzes

Question 1

Which of the following statements is not a law of thermodynamics?

Accepted Answer

Heat flows from cold to hot.

Answer

Energy cannot be created or destroyed.

Answer

The entropy of an isolated system always increases over time.

Question 2

The enthalpy change for a process at constant pressure is:

Accepted Answer

The heat transferred.

Answer

The work done.

Answer

The change in internal energy.

Question 3

Which of the following processes is isentropic?

Accepted Answer

Adiabatic expansion of an ideal gas.

Answer

Isothermal compression of a liquid.

Answer

Isochoric heating of a solid.

Answer

Isobaric cooling of a gas.

Question 4

The Joule-Thomson coefficient is a measure of:

Accepted Answer

The change in temperature of a gas upon adiabatic expansion.

Answer

The change in pressure of a gas upon adiabatic expansion.

Answer

The change in enthalpy of a gas upon adiabatic expansion.

Question 5

Which of the following is an example of a spontaneous process?

Accepted Answer

Melting of ice at room temperature.

Answer

Evaporation of water at 100°C.

Answer

Freezing of water at 0°C.

Question 6

What is the SI unit of entropy?

Accepted Answer

Joules per Kelvin

Answer

Kelvin

Answer

Calories per gram

Answer

Watts

Question 7

Which of the following processes releases heat to the surroundings?

Accepted Answer

Combustion of gasoline

Answer

Melting of ice

Answer

Boiling of water

Answer

Condensation of steam

Question 8

Which characteristic describes a spontaneous process?

Accepted Answer

Negative free energy change

Answer

Positive free energy change

Answer

Zero free energy change

Answer

Equal entropy change and enthalpy change

Question 9

Which mathematical expression represents the first law of thermodynamics?

Accepted Answer

dQ = dU + dW

Answer

dS = dH - TdS

Answer

dG = dH - TDS

Answer

dE = mcΔT

Question 10

Which thermodynamic potential determines the spontaneity of a reaction at constant temperature and pressure?

Accepted Answer

Gibbs free energy

Answer

Internal energy

Answer

Enthalpy

Answer

Free energy

Question 11

Which law of thermodynamics states that the entropy of an isolated system cannot decrease over time?

Accepted Answer

Second law

Answer

First law

Answer

Third law

Answer

Zeroth law

Question 12

The change in enthalpy of a system at constant pressure is equal to:

Accepted Answer

Heat transferred into the system

Answer

Work done by the system

Answer

Heat transferred out of the system

Answer

Work done on the system

Question 13

A spontaneous process is characterized by:

Accepted Answer

A decrease in free energy

Answer

An increase in free energy

Answer

A decrease in entropy

Answer

An increase in enthalpy

Question 14

The adiabatic compression of an ideal gas results in:

Accepted Answer

A decrease in temperature and an increase in pressure

Answer

A decrease in both temperature and pressure

Answer

An increase in both temperature and pressure

Answer

An increase in temperature and a decrease in pressure

Question 15

During the isothermal expansion of an ideal gas in a cylinder with a movable piston:

Accepted Answer

Work is done by the gas

Answer

No work is done by the gas

Answer

Work is done on the gas

Answer

The temperature of the gas increases

Question 16

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

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Concentration of reactants

Answer

Presence of a catalyst

Question 17

The equilibrium constant for a reaction is:

Accepted Answer

The ratio of the concentrations of products to the concentrations of reactants

Answer

The ratio of the forward reaction rate to the reverse reaction rate

Answer

The difference between the forward and reverse reaction rates

Answer

The sum of the forward and reverse reaction rates

Question 18

The standard free energy change for a reaction represents:

Accepted Answer

The free energy change under standard conditions

Answer

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

Answer

The free energy change under nonstandard conditions

Answer

The minimum amount of work that must be done to initiate the reaction

Question 19

Which of the following is a good indicator of the spontaneity of a reaction?

Accepted Answer

Free energy

Answer

Enthalpy

Answer

Entropy

Answer

Temperature

Question 20

The efficiency of a heat engine is defined as the:

Accepted Answer

Ratio of work output to heat input

Answer

Ratio of heat input to work output

Answer

Difference between work output and heat input

Answer

Sum of work output and heat input

Question 21

In thermodynamics, which of the following is a defining characteristic of an open system?

Accepted Answer

Mass and heat can both enter or leave the system.

Answer

No mass or heat can enter or leave the system.

Answer

Only mass can enter or leave the system.

Answer

Heat can enter or leave the system, but no mass can enter or leave.

Question 22

Which of the following statements correctly describes the first law of thermodynamics?

Accepted Answer

Energy cannot be created or destroyed, only transferred or transformed.

Answer

The free energy of a system always decreases during a spontaneous process.

Answer

The total entropy of an isolated system always increases over time.

Question 23

A system undergoes a process where it absorbs 100 J of heat and performs 50 J of work. What is the change in internal energy of the system?

Accepted Answer

50 J

Answer

150 J

Answer

-150 J

Answer

-50 J

Question 24

Which of the following processes is an example of an endothermic process?

Accepted Answer

Melting of ice

Answer

Freezing of water

Answer

Combustion of fuel

Answer

Condensation of steam

Question 25

The enthalpy change for a reaction is -50 kJ/mol. This indicates that the reaction is:

Accepted Answer

Exothermic

Answer

Endothermic

Answer

Isothermal

Question 26

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

Accepted Answer

0 kJ/mol

Answer

-1 kJ/mol

Answer

1 kJ/mol

Answer

Depends on the element

Question 27

Which of the following statements correctly describes entropy?

Accepted Answer

Entropy is a measure of the disorder or randomness of a system.

Answer

Entropy is a measure of the work done by a system.

Answer

Entropy is a measure of the energy content of a system.

Question 28

A spontaneous process is one that:

Accepted Answer

Occurs without external intervention

Answer

Always increases the enthalpy of the system

Answer

Always increases the entropy of the system

Answer

Always releases heat

Question 29

The Gibbs free energy change for a reaction is -10 kJ/mol. This indicates that the reaction is:

Accepted Answer

Spontaneous

Answer

At equilibrium

Answer

Endothermic

Answer

Non-spontaneous

Question 30

A reversible process is one that:

Accepted Answer

Can be reversed without any change in the surroundings

Answer

Always releases heat

Answer

Always increases the entropy of the system

Question 31

The efficiency of a heat engine is defined as:

Accepted Answer

The ratio of the work output to the heat input

Answer

The ratio of the heat input to the work output

Answer

The ratio of the heat input to the heat rejected

Answer

The ratio of the heat rejected to the work output