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15. The adiabatic elasticity of hydrogen gas (γ=1.4) at NTP is

(a) 1×105 N/m2 (b) 1×10-8 N/m2 (c) 1.4 N/m2 (d) 1.4×105 N/m2 Answer-d (8)

14. During the adiabatic expansion of 2 moles of a gas, the internal energy of the gas is found to decrease by 2 joules, the work done during the process on the gas will be equal to

(a) 1 J (b) -1 J (c) 2 J (d) – 2 J Answer-d (4)

6. A monoatomic gas (γ=5/3) is suddenly compressed to 1/8 of its original volume adiabatically, then the pressure of the gas will change to

(a) 24/5 (b) 8 (c) 40/3 (d) 32 times its initial pressure Answer-d (6)

23. When an ideal gas in a cylinder was compressed isothermally by a piston, the work done on the gas was found to be

1.5×104 J . During this process about (a) 3.6×103 cal of heat flowed out from the gas (b) 3.6×103 cal of heat flowed into the gas (c) 1.5×104 cal of heat flowed into the gas (d) 1.5×104 cal of heat …

10. Which is the correct statement

(a) For an isothermal change PV = constant (b) In an isothermal process the change in internal energy must be equal to the work done (c) For an adiabatic change P2/P1=(V2/V1)γ , where γ is the ratio of specific heats (d) …

8. An ideal gas at 27°C is compressed adiabatically to 8/27 of its original volume. If γ=5/3 , then the rise in temperature is

(a) 450 K (b) 375 K (c) 225 K (d) 405 K Answer-b (4)

9. Two identical samples of a gas are allowed to expand (i) isothermally (ii) adiabatically. Work done is

(a) More in the isothermal process (b) More in the adiabatic process (c) Neither of them (d) Equal in both processes Answer-a (8)

7. The pressure and density of a diatomic gas (γ=7/5) change adiabatically from (P, d) to (P’, d’). If (d’/d)=32 , then P’/P should be

(a) 1/128 (b) 32 (c) 128 (d) None of the above Answer-c (7)

5. A gas at NTP is suddenly compressed to one-fourth of its original volume.

If γ is supposed to be (3/2) , then the final pressure is (a) 4 atmosphere (b) 3/2 atmosphere (c) 8 atmosphere (d) 1/4 atmosphere Ans. c (7)

4. The pressure in the tyre of a car is four times the atmospheric pressure

at 300 K. If this tyre suddenly bursts, its new temperature will be ( γ=1.4) (a) 300 (4)1.4/0.4 (b) 300(1/4)-0.4/1.4 (c) 300(2)-0.4/1.4 (d) 300(4)-0.4/1.4 …

3. In adiabatic expansion

(a) ΔU = 0 (b) ΔU = negative (c) ΔU= positive (d) ΔW = zero Ans. b (8)

2. The work done in an adiabatic change in a gas depends only on

(a) Change is pressure (b) Change is volume (c) Change in temperature (d) None of the above Ans. a (7)

1. If a cylinder containing a gas at high pressure explodes, the gas undergoes

(a) Reversible adiabatic change and fall of temperature (b) Reversible adiabatic change and rise of temperature (c) Irreversible adiabatic change and fall of temperature (d) Irreversible adiabatic change and rise of temperature Answer-a (9)

31. During an isothermal expansion of an ideal gas

(a) Its internal energy decreases (b) Its internal energy does not change (c) The work done by the gas is equal to the quantity of heat absorbed by it (d) Both (b) and (c) are correct Ans. d (14)

40. The volume of an ideal gas is 1 litre and its pressure is equal to 72cm of mercury column.

The volume of gas is made 900 cm3 by compressing it isothermally. The stress of the gas will be (a) 8 cm (mercury) (b) 7 cm (mercury) (c) 6 cm (mercury) (d) 4 cm (mercury) Ans. a (5)

29. A cylinder fitted with a piston contains 0.2 moles of air at temperature

27°C. The piston is pushed so slowly that the air within the cylinder remains in thermal equilibrium with the surroundings. Find the approximate work done by the system if the final volume is twice the initial volume (a) 543 J …

28. One mole of an ideal gas expands at a constant temperature of 300 K from an initial volume of 10 litres to a final volume of 20 litres. The work done in expanding the gas is

(R = 8.31 J/mole–K) (a) 750 joules (b) 1728 joules (c) 1500 joules (d) 3456 joules Answer-b (12)

27. 540 calories of heat convert 1 cubic centimeter of water at 100°C into 1671 cubic centimeter of steam at 100°C at a pressure of one atmosphere. Then the work done against the atmospheric pressure is nearly

(a) 540 cal (b) 40 cal (c) Zero cal (d) 500 cal Answer-b (5)

26. The latent heat of vaporisation of water is 2240 J/gm. If the work done in the process of expansion of 1 g is 168 J, then increase in internal energy is

25. When 1 gm of water at 0°C and

1×105 N/m2 pressure is converted into ice of volume 1.091 cm3 , the external work done will be (a) 0.0091 joule (b) 0.0182 joule (c) – 0.0091 joule (d) – 0.0182 joule Answer-a (5)

24. When heat is given to a gas in an isothermal change, the result will be

(a) External work done (b) Rise in temperature (c) Increase in internal energy (d) External work done and also rise in temp. Answer-a (5)

22. If an ideal gas is compressed isothermally then

(a) No work is done against gas (b) Heat is relased by the gas (c) The internal energy of gas will increase (d) Pressure does not change Explanation-(b) In isothermal process, heat is released by the gas to maintain the …

21. A thermodynamic process in which temperature T of the system remains constant though other variable P and V may change, is called

(a) Isochoric process (b) Isothermal process (c) Isobaric process (d) None of these Explanation-(b) In isothermal process, temperature remains constant. (6)

20. In an isothermal process the volume of an ideal gas is halved. One can say that

(a) Internal energy of the system decreases (b) Work done by the gas is positive (c) Work done by the gas is negative (d) Internal energy of the system increases Answer-c (5)

19. A container that suits the occurrence of an isothermal process should be made of

(a) Copper (b) Glass (c) Wood (d) Cloth Explanation-(a) An isothermal process takes place at constant temperature, must be carried out in a vessel with conducting wall so that heat generated should go out at once. (7)

18. A thermally insulated container is divided into two parts by a screen. In one part the pressure and temperature are P and T for an ideal gas filled. In the second part it is vacuum. If now a small hole is created in the screen, then the temperature of the gas will

(a) Decrease (b) Increase (c) Remain same (d) None of the above Answer-c (10)

17. The specific heat of a gas in an isothermal process is

(a) Infinite (b) Zero (c) Negative (d) Remains constant Answer-a (12)

15. In isothermic process, which statement is wrong

(a) Temperature is constant (b) Internal energy is constant (c) No exchange of energy (d) (a) and (b) are correct Explanation-(c) In isothermal process, exchange of energy takes place between system and surrounding to maintain the system temperature constant. (13)