EASY
Earn 100

Define the following 

Root mean square velocity for the gas molecules.

Important Questions on Behaviour of Perfect Gases and Kinetic Theory of Gases

MEDIUM
An ideal gas is enclosed in a cylinder at pressure of 2 atm and temperature, 300 K. The mean time between two successive collisions is 6×10-8 s. If the pressure is doubled and temperature is increased to 500 K, the mean time between two successive collisions will be close to:
MEDIUM
Calculate the value of the mean free path λ for oxygen molecules at temperature 27°C and pressure 1.01×105 Pa. Assume the molecular diameter 0.3 nm and the gas is ideal. k=1.38×10-23 J K-1
MEDIUM
The mean free path for a gas at temperature 300 K and pressure 600 torr is 10-7 m. The mean free path of the gas at a temperature 400 K and pressure 200 torr will be
MEDIUM
A spring - block system is resting on a frictionless floor as shown in the figure. The spring constant is 2.0 N m-1 and the mass of the block is 2.0kg . Ignore the mass of the spring. Initially the spring is in an unstretched condition. Another block of mass 1.0kg moving with a speed of 2.0m s-1 collides elastically with the first block. The collision is such that the 2.0kg block does not hit the wall. The distance, in metres, between the two blocks when the spring returns to its unstretched position for the first time after the collision is _________.

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MEDIUM

An ideal gas in a closed container is slowly heated. As its temperature increases, which of the following statements are true ? 

(A) the mean free path of the molecules decreases

(B) the mean collision time between the molecules decreases.

(C) the mean free path remains unchanged.

(D) the mean collision time remains unchanged.

EASY
In a gas at STP, if n is the number density of the molecules and r is the radius of the molecule, then the mean free path of the molecule is inversely proportional to
EASY
If r is the radius of molecules in a gas, then the mean free path of molecules is proportional to
HARD
Particle A of mass mA=m2 moving along the x -axis with velocity v0 collides elastically with another particle B at rest having mass mB=m3. If both the particles move along the x -axis after the collision, the change λ in the wavelength of the particle A, in terms of its de-Broglie wavelength λ0 before the collision is:
EASY
The mean free path for a gas, with molecular diameter d and number density n can be expressed as:
EASY
A container is divided into two equal part I and II by a partition with small hole of diameter d. The two partitions are filled with same ideal gas, but held at temperature TI=150K and TII=300K by connecting to heat reservoirs. Let λI and λII be the mean free paths of the gas particles in the two parts such that d>>λI and d>>λII. Then λIλII is close to.
MEDIUM
In an ideal gas at temperature T, the average force that a molecule applies on the walls of a closed container depends on T as Tq . A good estimate for q is:
EASY
The mean free path of molecules of a gas (radius ‘ r ’) is inversely proportional to:
HARD
An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm. What will be length of the air column above mercury in the tube now ?
(Atmospheric pressure = 76 cm of Hg)
HARD

According to kinetic theory of gases,

A. The motion of the gas molecules freezes at 0°C.

B. The mean free path of gas molecules decreases if the density of molecules is increased.

C. The mean free path of gas molecules increases if temperature is increased keeping pressure constant.

D. Average kinetic energy per molecule per degree of freedom is 32kBT (for monoatomic gases).

Choose the most appropriate answer from the options given below

MEDIUM
Two gases - argon (atomic radius 0.07nm, atomic weight 40 ) and xenon (atomic radius 0.1nm, atomic weight 140 ) have the same number density and are at the same temperature. The ratio of their respective mean free times is closest to:
HARD

As shown schematically in the figure, two vessels contain water solutions (at temperature T) of potassium permanganate KMnO4 of different concentrations n1 and n2n1>n2 molecules per unit volume with Δn=n1-n2n1. When they are connected by a tube of small length l and cross-sectional area S, KMnO4 starts to diffuse from the left to the right vessel through the tube. Consider the collection of molecules to behave as dilute ideal gases and the difference in their partial pressure in the two vessels causing the diffusion. The speed v of the molecules is limited by the viscous force -βv on each molecule, where β is a constant. Neglecting all terms of the order Δn2. Which of the following is/are correct? (kB is the Boltzmann constant)

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MEDIUM
Initially a gas of diatomic molecules is contained in a cylinder of volume V1 at a pressure P1 and temperature 250 K. Assuming that 25% of the molecules get dissociated causing a change in number of moles. The pressure of the resulting gas at temperature 2000 K, when contained in a volume 2V1 is given by P2. The ratio P2/P1 is -
MEDIUM
The mean free path l for a gas molecule depends upon diameter, d of the molecule as:
HARD

Consider an ideal gas confined in an isolated closed chamber. As the gas undergoes an adiabatic expansion, the average time of collision between molecules increases as Vq , where V is the volume of the gas. The value of q is:

γ=CPCv

MEDIUM
The plot that depicts the behavior of the mean free time τ (time between two successive collisions) for the molecules of an ideal gas, as a function of temperature T, qualitatively, is: (Graphs are schematic and not drawn to scale)