Thermodynamics MCQs – CBSE Class 11 Chemistry

Thermodynamics MCQs – CBSE Class 11 Chemistry

Course: CBSE Class 11 Chemistry – MCQs with Answers and Explanations
Section: Physical Chemistry – MCQ Titles

The following 50 Multiple Choice Questions (MCQs) are strictly aligned with the NCERT chapter “Thermodynamics” for CBSE Class 11 Chemistry. The questions are arranged section-wise to ensure systematic coverage of concepts and include clear, concept-clearing explanations, making them ideal for board exam preparation and revision.

Section A: Introduction to Thermodynamics and Basic Terms

1. Thermodynamics mainly deals with the study of

A. reaction rates
B. energy changes in chemical processes
C. atomic structure
D. molecular geometry

Answer: B
Explanation: Thermodynamics focuses on energy changes accompanying physical and chemical processes.

2. The part of the universe under study is called

A. surroundings
B. system
C. boundary
D. phase

Answer: B
Explanation: The system is the portion selected for thermodynamic study.

3. Everything other than the system is known as

A. boundary
B. phase
C. surroundings
D. universe

Answer: C
Explanation: Surroundings include the rest of the universe except the system.

4. A system that can exchange both matter and energy with surroundings is

A. isolated system
B. closed system
C. open system
D. homogeneous system

Answer: C
Explanation: Open systems allow transfer of both matter and energy.

5. Which of the following is an isolated system?

A. Open beaker
B. Closed flask
C. Pressure cooker
D. Thermos flask

Answer: D
Explanation: An ideal thermos flask exchanges neither matter nor energy.

Section B: State Functions and Thermodynamic Properties

6. A property that depends only on the state of the system is called

A. path function
B. intensive property
C. extensive property
D. state function

Answer: D
Explanation: State functions depend only on initial and final states.

7. Which of the following is a state function?

A. Work
B. Heat
C. Enthalpy
D. Path length

Answer: C
Explanation: Enthalpy depends only on the state of the system.

8. Which of the following is an intensive property?

A. Mass
B. Volume
C. Internal energy
D. Temperature

Answer: D
Explanation: Intensive properties do not depend on the amount of substance.

9. Extensive properties depend on

A. temperature
B. pressure
C. amount of matter
D. nature of substance

Answer: C
Explanation: Extensive properties vary with the quantity of matter.

10. Which is NOT a state function?

A. Enthalpy
B. Internal energy
C. Heat
D. Entropy

Answer: C
Explanation: Heat depends on the path followed.

Section C: Internal Energy, Heat and Work

11. Internal energy of a system is denoted by

A. H
B. E or U
C. Q
D. W

Answer: B
Explanation: Internal energy is represented by U or E.

12. Change in internal energy depends on

A. path followed
B. initial and final states
C. pressure only
D. temperature only

Answer: B
Explanation: Internal energy is a state function.

13. Work done during expansion of gas is considered

A. positive
B. negative
C. zero
D. constant

Answer: B
Explanation: According to sign convention, work done by the system is negative.

14. Heat absorbed by the system is taken as

A. positive
B. negative
C. zero
D. undefined

Answer: A
Explanation: Heat absorbed increases system energy.

15. Which of the following is true for isothermal process?

A. Temperature changes
B. Pressure remains constant
C. Temperature remains constant
D. Volume remains constant

Answer: C
Explanation: In isothermal processes, temperature is constant.

Section D: First Law of Thermodynamics

16. The first law of thermodynamics is based on the law of

A. conservation of mass
B. conservation of energy
C. conservation of momentum
D. multiple proportions

Answer: B
Explanation: Energy is neither created nor destroyed.

17. Mathematical form of first law is

A. ΔE = q − w
B. ΔE = q + w
C. ΔE = w − q
D. ΔE = qw

Answer: A
Explanation: Change in internal energy equals heat absorbed minus work done.

18. If a system absorbs 500 J heat and does 200 J work, ΔE is

A. 300 J
B. −300 J
C. 700 J
D. −700 J

Answer: A
Explanation: ΔE = q − w = 500 − 200 = 300 J.

19. In an adiabatic process,

A. heat exchange occurs
B. temperature remains constant
C. no heat exchange occurs
D. pressure remains constant

Answer: C
Explanation: Adiabatic processes have no heat exchange.

20. For a cyclic process, change in internal energy is

A. positive
B. negative
C. zero
D. maximum

Answer: C
Explanation: System returns to initial state.

Section E: Enthalpy and Enthalpy Changes

21. Enthalpy (H) is defined as

A. U − PV
B. U + PV
C. q + w
D. w − q

Answer: B
Explanation: H = U + PV.

22. Enthalpy change at constant pressure is equal to

A. work done
B. heat absorbed
C. internal energy change
D. entropy change

Answer: B
Explanation: At constant pressure, ΔH = qₚ.

23. Enthalpy change for an exothermic reaction is

A. positive
B. zero
C. negative
D. infinite

Answer: C
Explanation: Heat is released, so ΔH is negative.

24. Enthalpy change depends on

A. path followed
B. catalyst
C. amount of substance
D. temperature only

Answer: C
Explanation: Enthalpy is an extensive property.

25. Standard enthalpy of formation is defined at

A. any temperature
B. 0 K
C. 1 atm pressure
D. standard conditions

Answer: D
Explanation: Standard enthalpy values are measured at standard conditions.

Section F: Hess’s Law and Reaction Enthalpies

26. Hess’s law is based on the concept that enthalpy is a

A. path function
B. state function
C. intensive property
D. kinetic property

Answer: B
Explanation: Enthalpy change is independent of path.

27. Hess’s law helps in calculating

A. reaction rate
B. entropy change
C. enthalpy change
D. equilibrium constant

Answer: C
Explanation: It allows indirect calculation of ΔH.

28. Enthalpy of combustion is always

A. positive
B. zero
C. negative
D. variable

Answer: C
Explanation: Combustion reactions release heat.

29. Enthalpy of neutralisation of strong acid and strong base is

A. −57 kJ mol⁻¹
B. −100 kJ mol⁻¹
C. +57 kJ mol⁻¹
D. 0

Answer: A
Explanation: Formation of one mole of water releases ~57 kJ.

30. Bond enthalpy is defined as energy required to

A. form a bond
B. break a bond
C. compress a bond
D. weaken a bond

Answer: B
Explanation: Bond enthalpy measures bond strength.

Section G: Entropy and Spontaneity

31. Entropy is a measure of

A. energy
B. randomness
C. enthalpy
D. heat

Answer: B
Explanation: Higher entropy means greater disorder.

32. Entropy increases when

A. gas condenses
B. solid melts
C. gas liquefies
D. temperature decreases

Answer: B
Explanation: Disorder increases on melting.

33. Which process has maximum entropy?

A. Solid
B. Liquid
C. Gas
D. Crystal

Answer: C
Explanation: Gases have maximum randomness.

34. A spontaneous process is one that

A. requires continuous energy
B. occurs naturally
C. never stops
D. is very fast

Answer: B
Explanation: Spontaneous processes occur without external intervention.

35. Increase in entropy favours

A. non-spontaneity
B. equilibrium only
C. spontaneity
D. stability

Answer: C
Explanation: Higher entropy increases spontaneity.

Section H: Gibbs Free Energy

36. Gibbs free energy is given by

A. G = H − TS
B. G = H + TS
C. G = U − TS
D. G = TS − H

Answer: A
Explanation: G combines enthalpy and entropy effects.

37. For a spontaneous process, ΔG should be

A. positive
B. zero
C. negative
D. maximum

Answer: C
Explanation: Negative ΔG indicates spontaneity.

38. At equilibrium, Gibbs free energy change is

A. positive
B. negative
C. zero
D. infinite

Answer: C
Explanation: No net driving force exists at equilibrium.

39. Endothermic reactions can be spontaneous when

A. ΔS is negative
B. ΔS is positive and large
C. temperature is zero
D. pressure is high

Answer: B
Explanation: Positive entropy can drive spontaneity.

40. Unit of entropy is

A. J
B. J mol⁻¹
C. J K⁻¹ mol⁻¹
D. kJ

Answer: C
Explanation: Entropy includes temperature in denominator.

Section I: Conceptual NCERT-Based MCQs

41. Which of the following processes is exothermic?

A. Melting of ice
B. Evaporation of water
C. Combustion of fuel
D. Sublimation of iodine

Answer: C
Explanation: Combustion releases heat.

42. Work done in free expansion of gas is

A. positive
B. negative
C. zero
D. maximum

Answer: C
Explanation: No external pressure, so no work is done.

43. Which quantity decides feasibility of a reaction?

A. Enthalpy
B. Entropy
C. Gibbs free energy
D. Internal energy

Answer: C
Explanation: ΔG determines spontaneity.

44. The SI unit of enthalpy is

A. joule
B. calorie
C. kelvin
D. pascal

Answer: A
Explanation: Enthalpy is a form of energy.

45. Which law introduces entropy?

A. First law
B. Second law
C. Third law
D. Zeroth law

Answer: B
Explanation: Second law deals with entropy and spontaneity.

46. Entropy of a perfect crystal at 0 K is

A. infinite
B. zero
C. maximum
D. negative

Answer: B
Explanation: Third law of thermodynamics.

47. Which thermodynamic quantity is always conserved?

A. Heat
B. Work
C. Energy
D. Entropy

Answer: C
Explanation: Total energy of universe is conserved.

48. Heat and work are called path functions because they depend on

A. temperature
B. pressure
C. initial state
D. path followed

Answer: D
Explanation: Their values change with the path.

49. Increase in temperature generally increases

A. enthalpy only
B. entropy only
C. both enthalpy and entropy
D. Gibbs energy

Answer: C
Explanation: Higher temperature increases energy and disorder.

50. Thermodynamics cannot predict

A. feasibility of reaction
B. energy change
C. rate of reaction
D. equilibrium condition

Answer: C
Explanation: Reaction rate is studied under chemical kinetics.

✅ Completion Note

This completes a fully NCERT-aligned, CBSE-standard set of 50 MCQs on Thermodynamics, ideal for concept clarity, systematic revision, and board exam preparation.