JEE Main - First law of thermodynamics work heat internal energy and enthalpy Online Test (MCQ Quiz)

1. Which of the following statements best describes the First Law of Thermodynamics?

A) Energy can be created but not destroyed. B) Energy can neither be created nor destroyed, only converted from one form to another. C) The total entropy of an isolated system can only decrease over time. D) Heat spontaneously flows from a colder body to a hotter body.

2. In thermodynamic terms, what is defined as the energy transferred between a system and its surroundings due to a temperature difference?

A) Work B) Internal Energy C) Enthalpy D) Heat

3. What does 'q' represent in the First Law of Thermodynamics equation, ΔU = q + w?

A) Work done by the system B) Heat absorbed by the system C) Change in internal energy D) Enthalpy change

4. What does 'w' represent in the First Law of Thermodynamics equation, ΔU = q + w, when work is done ON the system?

A) Work done by the system B) Heat absorbed by the system C) Work done on the system D) Enthalpy change

5. The change in internal energy (ΔU) of a system is dependent on:

A) The path taken between initial and final states B) The initial and final states only C) The amount of heat transferred only D) The amount of work done only

6. Which thermodynamic quantity is defined as the heat absorbed or released by a system at constant pressure?

A) Internal Energy B) Heat C) Work D) Enthalpy

7. For an exothermic process occurring at constant pressure, what is the sign of ΔH?

A) Positive B) Negative C) Zero D) Cannot be determined

8. For an endothermic process occurring at constant pressure, what is the sign of ΔH?

A) Negative B) Positive C) Zero D) Cannot be determined

9. In the equation ΔH = ΔU + PΔV, what does PΔV represent?

A) Work done by the system at constant volume B) Heat absorbed at constant pressure C) Work done by the system at constant pressure D) Change in internal energy

10. If a system absorbs 50 J of heat and does 20 J of work on the surroundings, what is the change in internal energy (ΔU)?

A) 70 J B) 30 J C) -30 J D) -70 J

11. If a system releases 100 J of heat and 30 J of work is done on the system, what is the change in internal energy (ΔU)?

A) -130 J B) -70 J C) 70 J D) 130 J

12. For an isochoric process (constant volume), the work done (w) is:

A) Zero B) Positive C) Negative D) Equal to ΔH

13. If ΔU = 0 for a process, what can be concluded about the heat and work exchanged?

A) q = w B) q = -w C) q = 0 D) w = 0

14. Which of the following is a state function in thermodynamics?

A) Heat B) Work C) Internal Energy D) Path

15. Which of the following is NOT a state function?

A) Enthalpy B) Internal Energy C) Heat D) Entropy

16. When is enthalpy change (ΔH) equal to the heat absorbed or released?

A) At constant volume B) At constant temperature C) At constant pressure D) During adiabatic processes

17. Consider a system where 200 J of work is done BY the system, and it absorbs 150 J of heat. What is the change in internal energy?

A) 350 J B) 50 J C) -50 J D) -350 J

18. If a chemical reaction has ΔH < 0, it is:

A) Endothermic and absorbs heat B) Exothermic and releases heat C) Neither endothermic nor exothermic D) An isobaric process

19. If a chemical reaction has ΔH > 0, it is:

A) Exothermic and releases heat B) Endothermic and absorbs heat C) An isochoric process D) A process with no heat transfer

20. What is the relationship between internal energy (U), enthalpy (H), pressure (P), and volume (V)?

A) H = U - PV B) U = H + PV C) H = U + PV D) PV = U + H

21. In the expansion of an ideal gas into a vacuum (free expansion), what are the values of heat (q) and work (w)?

A) q = 0, w ≠ 0 B) q ≠ 0, w = 0 C) q = 0, w = 0 D) q ≠ 0, w ≠ 0

22. For a free expansion of an ideal gas, ΔU is:

A) Positive B) Negative C) Zero D) Dependent on pressure

23. What is the sign of work done BY the system during expansion?

A) Positive B) Negative C) Zero D) Cannot be determined

24. What is the sign of work done ON the system during compression?

A) Positive B) Negative C) Zero D) Cannot be determined

25. If a process occurs at constant temperature and pressure, and the system expands, what is the sign of work?

A) Positive B) Negative C) Zero D) Cannot be determined

26. Which thermodynamic law is also known as the law of conservation of energy?

A) Zeroth Law B) First Law C) Second Law D) Third Law

27. Internal energy (U) is a function of:

A) Temperature and Pressure only B) Temperature only C) Pressure and Volume only D) Temperature and Volume only

28. For an ideal gas, the internal energy (U) depends only on:

A) Pressure B) Volume C) Temperature D) Number of moles

29. If ΔU is positive, it means the internal energy of the system has:

A) Decreased B) Increased C) Remained the same D) Become zero

30. Which of the following expressions correctly represents the work done by a gas during expansion against a constant external pressure?

A) w = -PΔV B) w = PΔV C) w = -ΔV/P D) w = ΔV

31. What is the enthalpy change for a process where ΔU = 100 kJ and PΔV = 30 kJ?

A) 70 kJ B) 130 kJ C) 100 kJ D) 30 kJ

32. What is the internal energy change for a process where ΔH = 50 kJ and PΔV = -15 kJ?

A) 65 kJ B) 35 kJ C) 50 kJ D) -15 kJ

33. In an adiabatic process, what is the heat transfer (q)?

A) Zero B) Positive C) Negative D) Equal to ΔH

34. For an adiabatic process, the First Law of Thermodynamics simplifies to:

A) ΔU = q B) ΔU = w C) ΔU = 0 D) ΔH = 0

35. If a system undergoes a cycle, returning to its initial state, what is the change in internal energy (ΔU) and enthalpy (ΔH)?

A) ΔU ≠ 0, ΔH ≠ 0 B) ΔU = 0, ΔH ≠ 0 C) ΔU ≠ 0, ΔH = 0 D) ΔU = 0, ΔH = 0

36. Which of the following is NOT a unit of energy or work?

A) Joule B) Calorie C) Pascal D) Erg

37. A system releases 80 J of heat and its internal energy increases by 40 J. How much work was done?

A) 40 J B) -40 J C) 120 J D) -120 J

38. When is ΔH equal to ΔU?

A) At constant pressure and constant volume B) At constant temperature C) When there is no change in the number of moles of gas D) During an adiabatic process

39. What is the definition of enthalpy?

A) The total energy of a system B) The heat content of a system C) The energy of a system plus the product of its pressure and volume D) The energy transferred as heat

40. Consider the reaction: N₂(g) + 3H₂(g) → 2NH₃(g). For this reaction, ΔH is related to ΔU by:

A) ΔH = ΔU B) ΔH = ΔU - 2RT C) ΔH = ΔU + 2RT D) ΔH = ΔU + RT

41. What does the term 'system' refer to in thermodynamics?

A) The universe excluding the surroundings B) A specific part of the universe under study C) Everything outside the boundary of the study D) The boundary itself

42. What defines the boundary between a system and its surroundings?

A) It must be permeable B) It must be rigid C) It is the interface separating the system from its surroundings D) It must be insulating

43. An open system can exchange with its surroundings:

A) Only energy B) Only matter C) Both energy and matter D) Neither energy nor matter

44. A closed system can exchange with its surroundings:

A) Only energy B) Only matter C) Both energy and matter D) Neither energy nor matter

45. An isolated system can exchange with its surroundings:

A) Only energy B) Only matter C) Both energy and matter D) Neither energy nor matter

46. If 500 calories of heat are supplied to a system, and the system does 1000 J of work, what is the change in internal energy (1 cal = 4.184 J)?

A) 2092 J B) 1092 J C) -1092 J D) 3092 J

47. Work done during reversible isothermal expansion of an ideal gas is given by:

A) -nRT log(V₂/V₁) B) -nRT log(P₂/P₁) C) PΔV D) nRT

48. For a reaction where the number of moles of gaseous products is greater than the number of moles of gaseous reactants (Δn_gas > 0), which relationship holds true?

A) ΔH < ΔU B) ΔH > ΔU C) ΔH = ΔU D) ΔH = ΔU + RT

49. For a reaction where the number of moles of gaseous products is less than the number of moles of gaseous reactants (Δn_gas < 0), which relationship holds true?

A) ΔH > ΔU B) ΔH < ΔU C) ΔH = ΔU D) ΔH = ΔU - RT

50. Which of the following scenarios would result in zero change in internal energy (ΔU = 0)?

A) A system absorbs heat and does work equal to the heat absorbed. B) A system releases heat and work is done on it. C) An adiabatic process where work is done on the system. D) A process at constant volume with heat absorbed.

First law of thermodynamics work heat internal energy and enthalpy - Online Test

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