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Q.1. Match column  I and column  II and choose the correct match from the given choices. [2021]
A: (A)  (Q), (B)  (P), (C)  (S), (D)  (R)
B: (A)  (R), (B)  (Q), (C)  (P), (D)  (S)
C: (A)  (R), (B)  (P), (C)  (S), (D)  (Q)
D: (A)  (Q), (B)  (R), (C)  (S), (D)  (P)
Ans: A
Root mean square speed of gas molecules
Q.2. A cylinder contains hydrogen gas at pressure of 249 kPa and temperature 27°C.
Its density is : (R = 8.3 J mol^{1} K^{1}) [2020]
A: 0.1 kg/m^{3}
B: 0.02 kg/m^{3}
C: 0.5 kg/m^{3}
D: 0.2 kg/m^{3}
Ans: D
∴ PV = nRT
Q.3. The mean free path for a gas, with molecular diameter d and number density n can be expressed as : [2020]
A:
B:
C:
D:
Ans: D
The mean free path for gas is given by
Q.4. Increase in temperature of a gas filled in a container would lead to: [2019]
A: Increase in its mass
B: Increase in its kinetic energy
C: Decrease in its pressure
D: Decrease in intermolecular distance
Ans: B
Solution: Increase in temperature would lead to the increase in kinetic energy of gas (assuming far as to be ideal) as
Q.5. At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the Earth's atmosphere ? (Given: Mass of oxygen molecule (m) = 2.76 × 10^{–26} kg Boltzmann's constant kB = 1.38 × 10^{–23} J K^{–1}): [2018]
A: 2.508 × 10^{4} K
B: 8.360 × 10^{4} K
C: 5.016 × 10^{4} K
D: 1.254 × 10^{4} K
Ans: B
Solution:
Q.6. The deBroglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T(Kelvin) and mass m, is: [2017]
A:
B:
C:
D:
Ans: A
Solution: Kinetic energy of thermal neutron with equilibrium
Q.7. A gas mixture consists of 2 moles of O_{2} and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is: [2017]
A: 15 RT
B: 9 RT
C: 11 RT
D: 4 RT
Ans: C
Solution:
Q.8. The molecules of a given mass of a gas have r.m.s. velocity of 200 ms^{1} at 27°C and 1.0 x 10^{5} Nm^{2} pressure. When the temperature and pressure of the gas are respectively, 127°C and 0.05 x 10^{5}Nm^{2}, the r.m.s. velocity of velocity of its molecules in ms^{1} is; [2016]
A: 100 / 3
B: 100 √2
C: 400 / √3
D: 100√2 / 3
Ans: C
Solution:
It is given that,
v_{rms} = 200 m/s
T_{1} = 300 K
P_{1} = 10^{5} N/m^{2}
rms velocity of gas molecules,
For two different cases,
It is given that,
v_{rms} = 200 m/s
T_{1} = 300 K
P_{1} = 10^{5} N/m^{2}
rms velocity of gas molecules,
For two different cases,
Q.9. The ratio of the specific heats in terms of degrees of freedom (n) is given by: [2015]
A:
B:
C:
D:
Ans: D
Solution:
This fits into the pattern , where n is the number of the degrees of freedom
Q.10. The mean free path of molecules of a gas,(radius ‘r’) is inversely proportional to: [2014]
A: r
B: √r
C: r^{3}
D: r^{2}
Ans: D
Solution:
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