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2. When heat in given to a gas in an isobaric process, then

(a) The work is done by the gas (b) Internal energy of the gas increases (c) Both (a) and (b) (d) None from (a) and (b) Answer-c (6)

1. A gas expands under constant pressure P from volume

V1 to V2. The work done by the gas is (a) P(V2-V1) (b) P(V1-V2) (c) P(V1γ-V2γ) (d) (PV1V2)/(V2-V1) Answer-a (6)

56. Adiabatic modulus of elasticity of a gas is

2.1×105N/m2. What will be its isothermal modulus of elasticity[(Cp/Cv)=1.4] (a) 1.8×105N/m2 (b) 1.5×105N/m2 (c) 1.4×105N/m2 (d) 1.2×105N/m2 Answer-b (14)

55. During an adiabatic expansion of 2 moles of a gas, the change in internal energy was found –50J. The work done during the process is

(a) Zero (b) 100J (c) – 50J (d) 50J Answer-d (8)

54. The volume of a gas is reduced adiabatically to 1/4 of its volume at 27°C, if the value of γ=1.4 then the new temperature will be

(a) 350×40.4 K (b) 300×40.4 K (c) 150×40.4 K (d) None of these Answer-b (2)

52. A gas for which γ=1.5 is suddenly compressed to 1/4th of the initial volume. Then the ratio of the final to the initial pressure is

(a) 1 : 16 (b) 1 : 8 (c) 1 : 4 (d) 8 : 1 Answer-d (3)

51. A gas is suddenly compressed to one fourth of its original volume. What will be its final pressure, if its initial pressure is P

(a) Lesss than P (b) More than P (c) P (d) Either (a) or (c) Answer-b (6)

50. We consider a thermodynamic system. If ΔU represents the increase in its internal energy and W the work done by the system, which of the following statements is true

(a) ΔU=-W in an adiabatic process (b) ΔU=W in an isothermal process (c) ΔU=-W in an isothermal process (d) ΔU=W in an adiabatic process Answer-a (2)

49. The internal energy of the gas increases In

(a) Adiabatic expansion (b) Adiabatic compression (c) Isothermal expansion (d) Isothermal compression Answer-b (5)

48. A gas ( γ=1.3) is enclosed in an insulated vessel fitted with insulating piston at a pressure of

105 N/m2 . On suddenly pressing the piston the volume is reduced to half the initial volume. The final pressure of the gas is (a) 20.7 ×105 (b) 21.3 ×105 …

47. A gas is suddenly compressed to 1/4 th of its original volume at normal temperature. The increase in its temperature is(γ=1.5)

(a) 273 K (b) 573 K (c) 373 K (d) 473 K Answer-a (6)

46. One mole of an ideal gas at an initial temperature of T K does 6 R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be

(a) (T+2.4)K (b) (T-2.4)K (c) (T+4)K (d) (T-4)K Answer-d (8)

45. In adiabatic expansion of a gas

(a) Its pressure increases (b) Its temperature falls (c) Its density increases (d) Its thermal energy increases Answer-b (5)

44.During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio

Cp/Cv for the gas is (a) 3/2 (b) 4/3 (c) 2 (d) 5/3 Answer-a (11)

43. In an adiabatic process, the state of a gas is changed from

(P1,V1,T1) to (P2,V2,T2) . Which of the following relation is correct (a) T1V1γ-1=T2V2γ-1 (b) P1V1γ-1=P2V2γ-1 (c) T1P1γ=T2P2γ (d) T1V1γ=T2V2γ Answer-a (10)

42. If γ=2.5 and volume is equal to 1/8 times to the initial volume then pressure P’ is equal to (Initial pressure = P)

(a) P‘=P (b) P‘=2P (c) P‘=P ×215/2 (d) P‘=7P Answer-c (8)

41. Air is filled in a motor tube at 27°C and at a pressure of atmospheres. The tube suddenly bursts, then temperature of air is( given γ of air=1.5)

(a) 27.5°C (b) 75°K (c) 150K (d) 150°C Answer-c (3)

40. An ideal gas at a pressures of 1 atmosphere and temperature of 27°C is compressed adiabatically until its pressure becomes 8 times the initial pressure, then the final temperature is (γ = 3/2)

(a) 627°C (b) 527°C (c) 427°C (d) 327°C Answer-d (12)

39. ΔU + ΔW =0 is valid for

(a) Adiabatic process (b) Isothermal process (c) Isobaric process (d) Isochoric process Answer-a (4)

38. At 27°C a gas is suddenly compressed such that its pressure becomes 1/8 th of original pressure. Temperature of the gas will be(γ=5/3)

(a) 420K (b) 327°C (c) 300K (d) -142°C …

37. Two moles of an ideal monoatomic gas at 27°C occupies a volume of V. If the gas is expanded adiabatically to the volume 2V then the work done by the gas will be (γ=5/3,R=8.31J/mol K)

(a) -2767.23 J (b) 2767.23 J (c) 2500J (d) -2500J Answer-b (3)

36. The process in which no heat enters or leaves the system is termed as

(a) Isochoric (b) Isobaric (c) Isothermal (d) Adiabatic Answer-(d) In adiabatic process, no transfer of heat takes place between system and surrounding. (4)

35. A gas is being compressed adiabatically. The specific heat of the gas during compression is

(a) Zero (b) Infinite (c) Finite but non-zero (d) Undefined Answer-a (6)

34. A diatomic gas initially at 18°C is compressed adiabatically to one-eighth of its original volume. The temperature after compression will be

(a) 10°C (b) 887°C (c) 668K (d) 144°C …

27. During the adiabatic expansion of 2 moles of a gas, the internal energy was found to have decreased by 100 J. The work done by the gas in this process is

(a) Zero (b) –100 J (c) 200 J (d) 100 J Ans. d (14)

26. A given system undergoes a change in which the work done by the system equals the decrease in its internal energy. The system must have undergone an

(a) Isothermal change (b) Adiabatic change (c) Isobaric change (d) Isochoric change Answer-b (7)

25. An ideal gas is expanded adiabatically at an initial temperature of 300 K so that its volume is doubled. The final temperature of the hydrogen gas is(γ=1.40)

(a) 227.36 K (b) 500.30 K (c) 454.76 K (d) -47°C Answer-a (5)

20. Compressed air in the tube of a wheel of a cycle at normal temperature suddenly starts coming out from a puncture. The air inside

(a) Starts becoming hotter (b) Remains at the same temperature (c) Starts becoming cooler (d) May become hotter or cooler depending upon the amount of water vapour present Answer-c (3)

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