First law of thermodynamics work heat internal energy and enthalpy - One Line Questions

1. 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)? — -70 J
2. Work done during reversible isothermal expansion of an ideal gas is given by: — -nRT log(V₂/V₁)
3. 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)? — 1092 J
4. 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? — -50 J
5. A system releases 80 J of heat and its internal energy increases by 40 J. How much work was done? — -120 J
6. What is the internal energy change for a process where ΔH = 50 kJ and PΔV = -15 kJ? — 35 kJ
7. 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)? — 30 J
8. What is the enthalpy change for a process where ΔU = 100 kJ and PΔV = 30 kJ? — 130 kJ
9. Which of the following scenarios would result in zero change in internal energy (ΔU = 0)? — A system absorbs heat and does work equal to the heat absorbed.
10. When is ΔH equal to ΔU? — When there is no change in the number of moles of gas
11. When is enthalpy change (ΔH) equal to the heat absorbed or released? — At constant pressure
12. If ΔU is positive, it means the internal energy of the system has: — Increased
13. If a chemical reaction has ΔH < 0, it is: — Exothermic and releases heat
14. Which of the following statements best describes the First Law of Thermodynamics? — Energy can neither be created nor destroyed, only converted from one form to another.
15. Which of the following is NOT a state function? — Heat
16. If a chemical reaction has ΔH > 0, it is: — Endothermic and absorbs heat
17. What is the relationship between internal energy (U), enthalpy (H), pressure (P), and volume (V)? — H = U + PV
18. Which of the following is a state function in thermodynamics? — Internal Energy
19. Which thermodynamic quantity is defined as the heat absorbed or released by a system at constant pressure? — Enthalpy
20. What defines the boundary between a system and its surroundings? — It is the interface separating the system from its surroundings
21. Which of the following is NOT a unit of energy or work? — Pascal
22. For an endothermic process occurring at constant pressure, what is the sign of ΔH? — Positive
23. An open system can exchange with its surroundings: — Both energy and matter
24. A closed system can exchange with its surroundings: — Only energy
25. An isolated system can exchange with its surroundings: — Neither energy nor matter
26. For an exothermic process occurring at constant pressure, what is the sign of ΔH? — Negative
27. For a free expansion of an ideal gas, ΔU is: — Zero
28. What is the sign of work done BY the system during expansion? — Negative
29. What is the sign of work done ON the system during compression? — Positive
30. If a process occurs at constant temperature and pressure, and the system expands, what is the sign of work? — Negative
31. For an ideal gas, the internal energy (U) depends only on: — Temperature
32. In the expansion of an ideal gas into a vacuum (free expansion), what are the values of heat (q) and work (w)? — q = 0, w = 0
33. If ΔU = 0 for a process, what can be concluded about the heat and work exchanged? — q = -w
34. Internal energy (U) is a function of: — Temperature only
35. The change in internal energy (ΔU) of a system is dependent on: — The initial and final states only
36. The enthalpy of a system is defined as: — The sum of its internal energy and the product of its pressure and volume.
37. What is the definition of enthalpy? — The energy of a system plus the product of its pressure and volume
38. What does the term 'system' refer to in thermodynamics? — A specific part of the universe under study
39. Which of the following expressions correctly represents the work done by a gas during expansion against a constant external pressure? — w = -PΔV
40. In thermodynamic terms, what is defined as the energy transferred between a system and its surroundings due to a temperature difference? — Heat
41. What does 'q' represent in the First Law of Thermodynamics equation, ΔU = q + w? — Heat absorbed by the system
42. What does 'w' represent in the First Law of Thermodynamics equation, ΔU = q + w, when work is done ON the system? — Work done on the system
43. In the equation ΔH = ΔU + PΔV, what does PΔV represent? — Work done by the system at constant pressure
44. For an isochoric process (constant volume), the work done (w) is: — Zero
45. In an adiabatic process, what is the heat transfer (q)? — Zero
46. Which thermodynamic law is also known as the law of conservation of energy? — First Law
47. 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? — ΔH > ΔU
48. Consider the reaction: N₂(g) + 3H₂(g) → 2NH₃(g). For this reaction, ΔH is related to ΔU by: — ΔH = ΔU - 2RT
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? — ΔH < ΔU
50. If a system undergoes a cycle, returning to its initial state, what is the change in internal energy (ΔU) and enthalpy (ΔH)? — ΔU = 0, ΔH = 0
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