1. OBJECTIVE QUESTIONS
FOR
NEET AIIMS JIPMER

2. Kinetic Theory Of Gases
PHYSICS
SET 1
MCQ’S

3. Q1. An inverted vessel (bell) lying at the bottom of a lake 47
Q1. An inverted vessel (bell) lying at the bottom of a lake 47.6 m deep has 50 cm3 of air trapped in it. The bell is brought to the surface of the lake the volume of the trapped air will now be : (Atmospheric pressure = 70 cm of mercury, density of mercury = 13.6 gm/cm3 and g = 980 cm/s2)
350 cm3
300 cm3
250 cm3
200 cm3

4. ANSWER (B)
EXPLANATION

5. Q2. Two gases A and B having the same temperature T, same pressure P and same volume V are mixed. If the mixture is at the same temperature T and occupies a volume V, the pressure of the mixture is :
2 P P
P/2
4 P

6. ANSWER (A)
EXPLANATION

7. Q3. Consider a 1 c.c. sample of air at absolute temperature T0 at sea level and another 1 c.c. sample of air at a height where the pressure is one-third atmosphere. The absolute temperature T of the sample at the height is :
Equal to T0/3
Equal to 3/T0
Equal to T0
Cannot be determined in terms of T0 from the above data

8. ANSWER (A)
EXPLANATION
Equal to T0/3

9. Q4. The relation PV = RT can describe the behavior of a real gets at
High temperature and high density
High temperature and low density
Low temperature and low density
Low temperature and high density

10. ANSWER (B)
EXPLANATION
A real gas can behave as an ideal gas at high temperature and low density.

11. Q5. If a given mass of gas occupies a volume of 100 c. c
Q5. If a given mass of gas occupies a volume of 100 c.c. at one atmospheric pressure and temperature of 100oC ( K). What will be its volume at 4 atmospheric pressure ; the temperature being the same ?
100 c.c.
400 c.c.
25 c.c
104 c.c

12. ANSWER (C)
EXPLANATION

13. Q6. What will be the volume of the above gas at two atmospheric pressure and at a temperature of K ?
100 c.c.
200 c.c
50 c.c
25 c.c

14. ANSWER (A)
EXPLANATION

15. Q7. The phenomenon of Brownian movement may be taken as evidence of
Kinetic theory of matter
Electromagnetic theory of radiation
Corpuscular theory of light
Photoelectric phenomenon

16. ANSWER (A)
EXPLANATION
The phenomenon of Brownian movement is related with the motion of molecules which is related to the kinetic theory of matter.

17. Q8. The molar gas constant is the same for all gases because at the same temperature and pressure equal volumes of gases have the same
Number of molecules
Average kinetic energy
Ratio of specific heats
Density

18. ANSWER (A)
EXPLANATION
Equal volume of all gases under identical conditions of pressure and temperature contain equal number of molecules.

19. Q9. The expansion of a mass m of an ideal gas at a constant pressure P is shown by the line H. The expansion of a mass 2 m of the same gas at pressure P/2 is shown by :
Line F
Line G
Line H
Line I

20. Here m PV = a constant, hence line H.
ANSWER (C)
EXPLANATION
Here m PV = a constant, hence line H.

21. Q10. Figure shows graphs of pressure versus density for an ideal gas at two temperature T1 and T2. Then from the graph
T1=T2
T1>T2
T1<T2
Nothing can be predicted

22. ANSWER (b)
EXPLANATION

23. Q11. We have a jar A filled with gas characterized by the parameters P, V and T and another jar B filled with a gas with parameters 2 P, V/4 and 2 T, where the symbols have their usual meanings. The ratio of the no. of molecules of jar A to those of jar B is :
1 : 1
1: 2
2 : 1
4 : 1

24. ANSWER (D)
EXPLANATION

25. Q12. Air is filled at 60oC in a vessel of open mouth
Q12. Air is filled at 60oC in a vessel of open mouth. The vessel is heated to a temperature T so that 1/4th part of air escapes. Assuming the volume of the vessel remaining constant, the value of T is :
80oC
143 oC
333 oC
416 oC

26. ANSWER (B)
EXPLANATION

28. ANSWER (C)
EXPLANATION

29. Q14. If the pressure in a closed vessel is reduced by drawing out some gas, the mean-free path of the molecules
Is decreased
Is increased
Remains unchanged
Increases or decreases according to the nature of the gas

30. ANSWER (B)
EXPLANATION
When pressure in a vessel is reduced, the molecules of the gas in vessel will find more distance to travel before colliding with other molecules.it means mean free path of molecules increases.

31. Q15. A box contains n molecules of a gas
Q15. A box contains n molecules of a gas. How will the pressure of the gas be affected if the number of molecules is made 2 n ?
Pressure will decrease
Pressure will remain unchanged
Pressure will be doubled
Pressure will become three times

32. ANSWER (C)
EXPLANATION

33. Q16. N molecules, each of mass m, of gas A and 2 N molecules, each of mass 2 m, of gas B are contained in the same vessel which is maintained at a temperature T. The mean square velocity of molecules of B type is denoted by V2 and the mean square velocity of A type is denoted by V1, then 𝑽 𝟏 𝑽 𝟐 is : 2 1
1/3
2/3

34. ANSWER (B)
EXPLANATION

35. Q17 Calculate the r.m.s. speed of smoke particles each of mass 𝟓× 𝟏𝟎 −𝟏𝟕 𝒌𝒈 in their Brownian motion in air at N.T.P. (𝒌=𝟏.𝟑𝟖× 𝟏𝟎 −𝟐𝟑 𝒋/𝒌)
1.5 mm/sec
1.5 m/sec
1.5 cm/sec
1.5 km/sec

36. ANSWER (C)
EXPLANATION

37. Q18. A gas at certain volume and temperature has a pressure equal to 75 cm of Hg column. If the mass of the gas is doubled, at the same volume and temperature, its new pressure is :
37.5 cm
75 cm
150 cm
300 cm

38. ANSWER (C)
EXPLANATION

39. Q19. The temperature of an ideal gas is increased from 120 K to 480 K
Q19. The temperature of an ideal gas is increased from 120 K to 480 K. if at 120 K, the root mean square velocity of gas molecules is v at 480 K it becomes
4 v
2 v
V/2
v/4

40. ANSWER (B)
EXPLANATION

41. Q20. Gas exerts pressure on the walls of the container because
Gas has weight
Gas molecules have momentum
Gas molecules collide with each other
Gas molecules collide with the walls of the container

42. ANSWER (D)
EXPLANATION
The collision of the gas molecules with the walls of the container causes change in momentum which accounts for the pressure exerted by gas on the walls.