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

NEET AIPMT Physics Chapter Wise SolutionsBiology 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 = 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 = **

(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 P _{1} and P_{2}?**

**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 for the gas is**

**14. The amount of heat energy required to raise the temperature of 1 g of Helium at NTP, from T _{1}K to T_{2}K 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 dQ_{1} = 50 J and the work obtained dW_{1} = 20 J whereas along the path abc the heat absorbed dQ_{2} = 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 T _{1 }and 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 T_{2}. 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 × 10^{4} 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 P _{1} and volume V_{1} is compressed adiabatically to of its original volume. What is the final pressure of the gas?**

(a) 64 P

_{1}(b) P

_{1}(c) 16 P

_{1}(d) 32 P

_{1}**(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 10 ^{4} 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 α _{1} and α_{2} respectively. When we take a brass rod of length l_{1} and steel rod of length l_{2} at 0°C, then difference in their lengths ( l_{2}– l_{1}) 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/m ^{2} 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/m

^{2}min

(b) 40 kcal/m

^{2}min

(c) 160 kcal/m

^{2}min

(d) 80 kcal/m

^{2}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 V _{1} to V_{2}. 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)**

**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, = 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,}m_{2} and m_{3} and the number of molecules in their respective containersare N_{1}, N_{2}, and N_{3} The gas pressure in the containers are P_{1,} P_{2} and P_{3} 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 1o ^{4} Pa; VA = 2 x 10**

^{-3}

**m**

PB = 8 x 10

^{3};PB = 8 x 10

^{4}Pa; VD = 5 x 10^{-3}

**m**

^{3}.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)**

### Explanations