NEET AIPMT Physics Chapter Wise Solutions - Thermodynamics and Kinetic Theory Archives

NEET AIPMT Physics Chapter Wise Solutions -Thermodynamics and Kinetic Theory

NEET AIPMT Physics Chapter Wise Solutions Biology Chemistry

1. An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas?
(a) Isochoric
(b) Isothermal
(c) Adiabatic
(d) Isobaric (A1PMT 2015)

2. Two vessels separately contain two ideal gases A and B at the same temperature, the pressure of A being twice that of B. Under such conditions, the density of A is found to be 1.5 times the density of B. The ratio of molecular weight of A and B is

3. The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20°C, the temperature of the surroundings to which it rejects heat is
(a) 11°C
(b) 21°C
(c) 31°C
(d) 41 °C (AIPMT 2015)

4. The ratio of the specific heats $\frac { cp }{ cv }$ = γ in terms of degrees of freedom (n) is given by

5. A Camot engine, having an efficiency of as heat engine, is used as a refrigerate. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is
(a) 90 J
(b) 1 J
(c) 100 J
(d) 99 J (AIPMT 2015, Cancelled)

6. One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure.

7. Figure below shows two paths that may be taken by a gas to go from a state A to a state C.

In process AB, 400 J of heat is added to the system and in process BC, 100 J of heat is added to the system. The heat absorbed by the system in the process AC will be
(a) 460 J
(b) 300 J
(c) 380 J
(d) 500 J (AIPMT 2015, Cancelled)

8. A monoatomic gas at a pressure P, having a . volume Pexpands isothermally to a volume 2V and then adiiabatically to a volume 16 V. The final pressure of the gas is (Take γ = $\frac { 5 }{ 3 }$
(a) 64P
(b) 32P
(c) P/64
(d) 16P (AIPMT 2014)

9. A thermodynamic system undergoes cyclic process ABCDA as shown in figure. The work done by the system in the cycle is

10. The mean free path of molecules of a gas, (radius r) is inversely proportional to

11. In the given (V – T) diagram,, what is the relation between pressures P₁ and P₂?

12. A gas is taken through the cycle A —> B —> C —> A, as shown. What is the net work done by the gas?

(a) Zero
(b) -2000 J
(c) 2000 J
(d) 1000 J (NEET 2013)

13. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its temperature, the retio of $\frac { cp }{ cv }$ for the gas is

14. The amount of heat energy required to raise the temperature of 1 g of Helium at NTP, from T₁K to T₂K is

15. A system is taken fromstate a to state c by two paths adc and abc as shown in the figure. The internal energy at a is U_a = 10 J. Along the path adc the amount of heat heat absorbed dQ₁ = 50 J and the work obtained dW₁ = 20 J whereas along the path abc the heat absorbed dQ₂ = 36 J. The amount of work along the path abc is

16. Which of the following relations does not give the equation of an adiabatic process, where terms have their usual meaning?

17. Two Camot engines A and B are operated in series. The engine A receives heat from the source at temperature T₁and rejects the heat to the sink at temperature T. The second engine B receives the heat at temperature T and rejects to its sink at temperature T₂. For what value of T the efficiencies of the two engines are equal

18. In a vessel, the gas is at pressure P. If the mass of all the molecules is halved and their speed is doubled, then the resultant pressure will be

19. A thermodynamic system is taken through the cycle ABCD as shown in figure. Heat rejected by the gas during the cycle is

(a) 2PV
(b) 4PV
(c) PV
(d) PV (Prelims 2012)

20. One mole of an ideal gas goes from an initial state A to final state B via two processes : It first undergoes isothermal expansion from volume V to 3 V and then its volume is reduced from 3V to V at constant pressure. The correct P-V diagram representing the two processes is

21. An ideal gas goes from state A to state B via three different processes as indicated in the P-V diagram.

22. During an isothermal expansion, a confined ideal gas does —150 J of work against its surroundings. This implies that
(a) 150 J of heat has been removed from the gas
(b) 300 J of heat has been added tV the gas
(c) no heat is transferred because the process is isothermal
(d) 150 J of heat has been added to the gas (Prelims 2011)

23. When 1 kg of ice at 0°C melts to water at 0°C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/°C, is
(a) 273 cal/K
(b) 8 × 10⁴ cal/K
(c) 80 cal/K
(d) 293 cal/K (Prelims 2011)

24. A mass of diatomic gas (γ= 1.4) at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 27°C to 927°C. The pressure of the gas in the -final state is
(a) 8 atm
(b) 28 atm
(c) 68.7 atm
(d) 256 atm (Mains 2011)

25. If Δu and ΔW represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?
(a) Δu= -ΔW, in a adiabatic process
(b) Δu=ΔW, in a isothermal process
(c) Δu = ΔW, in a adiabatic proass
(d) Δu= -ΔW,inu isothermal process (Prelims 2010)

26. If c_p and c_v denote the specific heats (per unit mass of an ideal gas of molecular weight M, then

27. A monoatomic gas at pressure P₁ and volume V₁ is compressed adiabatically to $\frac { 1 }{ 8 }$ of its original volume. What is the final pressure of the gas?
(a) 64 P₁
(b) P₁
(c) 16 P₁
(d) 32 P₁ (Mains 2010)

28. The internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work is
(a) 6400 J
(b) 5400 J
(c) 7900 J
(d) 8900 J (Prelims 2009)

29. In thermodynamic processes which of the following statements is not true?
(a) In an isochoric process pressure remains constant.
(b) In an isothermal process the temperature remains constant.
(c) In an adiabatic process PVγ = constant.
(d) In an adiabatic process the system is insulated from the surroundings. (Prelims 2009)

30. At 10°C the value of the density of a fixed mass of an ideal gas divided by it pressure is x. At 110°C this ratio is

31. If Q, E and W denote respectively the heat added, change in internal energy and the work done in a closed cycle process, then
(a) E = 0
(b) 0 = 0
(c) W=0
(d) Q=W= 0 (Prelims 2008)

32. An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62°C, its efficiency is doubled. Temperatures of the source is
(a) 37°C
(b) 62°C
(c) 99°C
(d) 124°C. (2007)

33. A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?
(a) 380 K
(b) 275 K
(c) 325 K
(d) 250 K. (2006)

34. The molar specific heat at constant pressure of an ideal gas is (7/2)R. The ratio of specific heat at constant pressure to that at constant volume is

35. An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 x 10⁴ cal of heat at higher temperature. Amount of heat converted to work is

36. Which of the following processes is reversible?
(a) Transfer of heat by conduction
(b) Transfer of heat by radiation
(c) Isothermal compression
(d) Electrical heating of a nichrome wire. (2005)

37. The equation of state for 5 g of oxygen at a pressure P and temperature P, when occupying a volume V, will be

38. One mole of an ideal gas at an initial temperature of T K does 6R joule 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

39. An ideal gas heat engine operates in a Carnot cycle between 227°C and 127°C. It absorbs 6 kcal at the higher temperature. The amount of heat (in kcal) converted into work is equal to
(a) 4.8
(b) 3.5
(c) 1.6
(d) 1.2 (2003)

40. The efficiency of Carnot engine is 50% and temperature of sink is 500 K. If temperature of source is kept constant and its efficiency raised to 60%, then the required temperature of sink will be
(a) 100 K
(b) 600 K
(c) 400 K
(d) 500 K. (2002)

41. A scientist says that the efficiency of his heat engine which work at source temperature 127°C and sink temperature 27°C is 26%, then
(a) it is impossible
(b) it is possible but less probable
(c) it is quite probable
(d) data are incomplete. (2001)

42. The (WIQ) of a Carnot engine is 1/6, now the temperature of sink is reduced by 62°C, then this ratio becomes twice, therefore the initial temperature of the sink and source are respectively
(a) 33°C, 67°C
(b) 37°C,99°C
(c) 67°C, 33°C
(d) 97 K, 37 K. (2000)

43. To find out degree of freedom, the expression is

44. An ideal gas at 27°C is compressed adiabatically to 8/27 of its original volume. The rise in temperature is (Take γy = 5/3)
(a) 275 K
(b) 375 K
(c) 475 K
(d) 175 K (1999)

45. If 1 g of steam is mixed with 1 g of ice, then resultant temperature of the mixture is
(a) 100°C
(b) 230°C
(c) 270°C
(d) 50°C (1999)

46. The coefficient of linear expansion of brass and steel are α₁ and α₂ respectively. When we take a brass rod of length l₁ and steel rod of length l₂ at 0°C, then difference in their lengths ( l₂– l₁) will remain the same at some temperature, if

47. The degrees of freedom of a triatomic gas is
(a) 6
(b) 4
(c) 2
(d) 8 (1999)

48. If the ratio of specific heat of a gas at constant pressure to that at constant volume is γ, the change in internal energy of a mass of gas, when the volume changes from Vto 2 Fat constant pressure P, is

49. The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/m² min. What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one?
(a) 320 kcal/m² min
(b) 40 kcal/m² min
(c) 160 kcal/m² min
(d) 80 kcal/m² min (1998)

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 isothermal process
(b) ΔU = W in an isothermal process
(c) ΔU = -W in an adiabatic process
(d) ΔU = W in an adiabatic process (1998)

51. The efficiency of a Camot engine operating with reservoir temperature of 100°C and – 23°C will be

52. A sample of gas expands from volume V₁ to V₂. The amount of work done by the gas is greatest, when the expansion is
(a) adiabatic
(b) equal in all cases
(c) isothermal
(d) isobaric. (1997)

53. The value of critical temperature in terms of van der Waals constant a and b is given by

54. An ideal gas, undergoing adiabatic change, has which of the following pressure temperature relationship?

55. A diatomic gas initially at 18°C is compressed adiabatically to one eighth of its original volume. The temperature after compression will be
(a) 395.4°C
(b) 144°C
(c) 18°C
(d) 887.4°C. (1996)

56. At 0 K which of the following properties of a gas will be zero?
(a) vibrational energy
(b) density
(c) kinetic energy
(d) potential energy. (1996)

57. An ideal Camot engine, whose efficiency is 40%, receives heat at 500 K. If its efficiency is 50%, then the intake temperature for the same exhaust temperature is
(a) 800 K
(b) 900 K
(c) 600 K
(d) 700 K. (1995)

58. In an adiabatic change, the pressure and temperature of a monatomic gas are related as P α T^c, where C equals

59. Which of the following is not thermodynamical function ?
(a) Enthalpy
(b) Work done
(c) Gibb’s energy
(d) Internal energy (1993)

60. 110 joule of heat is added to a gaseous system whose internal energy is 40 J, then the amount of external work done is
(a) 150 J
(b) 70 J
(c) 110 J
(d) 40 J (1993)

61. An ideal gas A and a real gas B have their volumes increased from V to 2 V under isothermal conditions. The increase in internal energy
(a) will be same in both A and B
(b) will be zero in both the gases
(c) of B will be more than that of A
(d) of A will be more than that of B (1993)

62. The number of transitional degrees of freedom for a diatomic gas is
(a) 2
(b) 3
(c) 5
(d) 6 (1993)

63. A thermodynamic system is taken from state A to B along ACB and is brought back to A along BDA as shown in the PV diagram. The net work done during the complete cycle is given- by the area

64. If for a gas, $\frac { R }{ cv }$ = 0.67, this gas is made up of molecules which are
(a) diatomic ‘
(b) mixture of diatomic and polyatomic molecules
(c) monoatomic
(d) polyatomic (1992)

65. For hydrogen gas C_p -C_v= a and for oxygen gas C_p – C_v= 6, so the relation between a and b is given by
(a) a = 166
(b) 166 = a
(c) a =46
(d) a = 6 (1991)

66. Three containers of the same volume contain three different gases. The masses of the molecules are m_1,m₂ and m₃ and the number of molecules in their respective containersare N₁, N₂, and N₃ The gas pressure in the containers are P_1, P₂ and P₃ respectively. All the gases are now mixed and put in one these containers. The pressure P of the mixture will be

67. A thermodynamic process is shown in the figure. The pressure and volumes corresponding to . some points in the figure are
PA = 3 x 1o⁴ Pa; VA = 2 x 10^-3m³;
PB = 8 x 10⁴ Pa; VD = 5 x 10^-3m³.

In the process AB, 600 J ofheat is added to the systemand in process BC, 200 J of heat is added to the system.The change in internalenergy of the system isprocess AC would be
(a) 560 J
(b) 800 J
(c) 600 J
(d) 640 J (1991)

68. Relation between pressure (P) and energy (E) of a gas is

69. One mole of an ideal gas requires 207 J heat to rise the temperature by 10 K when heated at 5 constant pressure. If the same gas is heated at constant volume to raise the temperature by the same 10 K, the heat required is (Given the gas constant R = 8.3 J/moleK)
(a) 198.7 J
(b) 29 J
(c) 215.3 J
(d) 124 J (1990)

70. Thermal capacity of 40 g of aluminum (s = 0.2 cal/g K) is
(a) 168 J/K
(b) 672 J/K
(c) 840 J/K
(d) 33.6 J/K (1996)

71. According to kinetic theory of gases, at absolute zero of temperature
(a) water freezes
(b) liquid helium freezes
(c) molecular motion stops
(d) liquid hydrogen freezes (l990)

72. For a certain gas the ratio of specific heats is given to be γ = 1.5. For this gas
(a) C_V = 3 R/J
(b) C_p = 3 R/J
(c) C_p= 5 R/J
(d) C_V = 5 R/J (1990)

73. A polyatomic gas with n degrees of freedom has a mean energy per molecule given by

74. At constant volume temperature is increased then
(a) collision on walls will be less
(b) number of collisions per unit time will increase
(c) collisions will be in straight lines
(d) collisions will not change (1989)

75. Two containers A and B are partly filled with water and closed. The volume of A is twice that of B and it contains half the amount of Water in B. If both are at the same temperature, the water vapour in the containers will have pressure in the ratio of
(a) 1 : 2
(b) 1 : 1
(c) 2 : 1
(d) 4 : 1 (1988)

76. 10 gm of ice cubes at 0° C are released in a tumbler (water equivalent 55 g) at 40° C. Assuming that negligible heat is taken from the surroundings, the temperature of water in the tumbler becomes nearely (L = 80 cal/g)
(a) 31 °C
(b) 22 °C
(c) 19 °C
(d) 15 °C (1988)

77. First law of thermodynamics is consequence of conservation of
(a) work
(b) energy
(c) heat
(d) all of these (1988)