July, 2022Flame Institute

41. The gas equation (PV)/T constant is true for a constant mass of an ideal gas undergoing

(a) Isothermal change (b) Adiabatic change (c) Isobaric change (d) Any type of change Answer-d (6)

39. At 100 K and 0.1 atmospheric pressure, the volume of helium gas is 10 litres. If volume and pressure are doubled, its temperature will change to

(a) 400 K (b) 127 K (c) 200 K (d) 25 K Answer-a (3)

36. When the pressure on 1200 ml of a gas in increased from 70 cm to 120 cm of mercury at constant temperature, the new volume of the gas will be

(a) 700 ml (b) 600 ml (c) 500 ml (d) 400 ml Answer-a (4)

34. At constant temperature on increasing the pressure of a gas by 5% will decrease its volume by

(a) 5% (b) 5.26% (c) 4.26% (d) 4.76% Answer-d (2)

33. Hydrogen gas is filled in a balloon at 20°C. If temperature is made 40°C , pressure remaining same, what fraction of Hydrogen will come out

(a) 0.07 (b) 0.25 (c) 0.5 (d) 0.75 Answer-a (7)

19. If pressure of a gas contained in a closed vessel is increased by 0.4% when heated by 1°C, the initial temperature must be

(a) 250 K (b) 250°C (c) 2500 K (d) 25°C Answer-a (5)

20. Consider a 1 c.c. sample of air at absolute temperature

T0 at sea level and another 1 cc sample of air at a height where the pressure is one-third atmosphere. The absolute temperature T of the sample at that height is (a) Equal to T0/3 (b) Equal to 3/T0 (c) …

22. Which of the following statements about kinetic theory of gases is wrong

(a) The molecules of a gas are in continuous random motion (b) The molecules continuously undergo inelastic collisions (c) The molecules do not interact with each other except during collisions (d) The collisions amongst the molecules are of short duration …

40. Under which of the following conditions is the law PV = RT obeyed most closely by a real gas

(a) High pressure and high temperature (b) Low pressure and low temperature (c) Low pressure and high temperature (d) High pressure and low temperature Answer-c (2)

38. The molecular weights of

O2 and N2 are 32 and 28 respectively. At 15°C, the pressure of 1 gm O2 will be the same as that of 1 gm N2 in the same bottle at the temperature (a) – 21°C (b) 13°C (c) 15°C …

37. The equation for an ideal gas is PV = RT, where V represents the volume of

(a) 1 gm gas (b) Any mass of the gas (c) One gm mol gas (d) One litre gas Answer-c (7)

35. Which law states that effect of pressure is same for all portion

(a) Pascal’s law (b) Gallusac’s law (c) Dalton’s law (d) None of these Answer-a (10)

32. A perfect gas at 27°C is heated at constant pressure to 327°C. If original volume of gas (at 27°C is V then volume at 327°C is

(a) V (b) 3 V (c) 2 V (d) V / 2 Answer-c (3)

31.

On 0°C pressure measured by barometer is 760 mm. What will be pressure on 100°C (a) 760 mm (b) 730 mm (c) 780 mm (d) None of these Answer-d (0)

21. To double the volume of a given mass of an ideal gas at 27°C keeping the pressure constant, one must raise the temperature in degree centigrade to

(a) 54° (b) 270° (c) 327° (d) 600° …

23. If a Vander-Waal’s gas expands freely, then final temperature is

(a) Less than the initial temperature (b) Equal to the initial temperature (c) More than the initial temperature (d) Less or more than the initial temperature depending on the nature of the gas Answer-a (28)

24. In Vander Waal’s equation

[P+(a/V2)](V-b)=RT, the dimensions of a are (a) M1L5 T-2 (b) M0 L2 T-1 (c) M1 L3 T-2 …

25. At NTP, sample of equal volume of chlorine and oxygen is taken. Now ratio of No. of molecules

(a) 1 : 1 (b) 32 : 27 (c) 2 : 1 (d) 16 : 14 Answer-a (5)

27. A cylinder of 5 litre capacity, filled with air at N.T.P. is connected with another evacuated cylinder of 30 litres of capacity. The resultant air pressure in both the cylinders will be

(a) 38.85 cm of Hg (b) 21.85 cm of Hg (c) 10.85 cm of Hg (d) 14.85 cm of Hg Answer-c (14)

28. Volume of gas become four times if

(a) Temperature become four times at constant pressure (b) Temperature become one fourth at constant pressure (c) Temperature becomes two times at constant pressure (d) Temperature becomes half at constant pressure Answer-a (5)

29. The relationship between pressure and the density of a gas expressed by Boyle’s law, P = KD holds true

(a) For any gas under any conditions (b) For some gases under any conditions (c) Only if the temperature is kept constant (d) Only if the density is constant Answer-c (39)

18. For Boyle’s law to hold the gas should be

(a) Perfect and of constant mass and temperature (b) Real and of constant mass and temperature (c) Perfect and at constant temperature but variable mass (d) Real and at constant temperature but variable mass Answer-a (4)

30. Kinetic theory of gases provide a base for

(a) Charle’s law (b) Boyle’s law (c) Charle’s law and Boyle’s law (d) None of these Answer-c (5)

17. The mean free path of gas molecules depends on (d = molecular diameter)

(a) d (b) d2 (c) d-2 (d) d-1 Answer-c (7)

16. When air is filled in the balloon, the pressure and volume both increases while temperature does not change. Here Boyle’s law is not obeyed because

(a) Mass of air is negligible (b) Mass of air does not remain constant (c) Air is not perfect gas (d) Pressure inside the balloon is less than that of the atmospheric pressure Answer-b (4)