EASY
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For a gas with n number of molecules per unit volume, Suppose the molecules of a gas are spheres of diameter d  the average speed of each molecule is v. The time between two successive collisions is on the average Γ=1nπvd2

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Important Questions on Kinetic Theory

MEDIUM
The mean free path l for a gas molecule depends upon diameter, d of the molecule as:
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)
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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HARD
A system consists of two types of gas molecules A and B having the same number density 2×1025 m-3. The diameter of A and B are 10A and 5A respectively. They suffer collisions at room temperature. The ratio of average distance covered by the molecule A to that of B between two successive collisions is ___________×10-2
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
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

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
Which of the following shows the correct relationship between the pressure 'P' and density ρ of an ideal gas at constant temperature ?
MEDIUM
If 1022 gas molecules each of mass 10-26 kg collides with a surface (perpendicular to it) elastically per second over an area 1 m2 with a speed 104m/s, the pressure exerted by the gas molecules will be of the order of:
EASY
The mean free path of molecules of a gas (radius ‘ r ’) is inversely proportional to:
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

Match Column - I and Column - II and choose the correct match from the given choices.

Column - I Column - II
(A) Root mean square speed of gas molecules  (P)13nmv2
(B) Pressure exerted by ideal gas Q 3RTM
(C) Average kinetic energy of a molecule R52RT
(D) Total internal energy of 1 mol of a diatomic
gas
S32kBT

 

EASY
On the basis of kinetic theory of gases, the gas exerts pressure because its molecules:
EASY
If r is the radius of molecules in a gas, then the mean free path of molecules is proportional to
EASY
Relationship between pressure P and kinetic energy (K.E.) of ideal gas is
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 25×10-3 m3 volume cylinder is filled with 1 mol of O2 gas at room temperature (300 K) . The molecular diameter of O2 , and its root mean square speed, are found to be 0.3 nm and 200 m s-1 , respectively. What is the average collision rate (per second) for an O2 molecule?
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:
EASY
The RMS speed of oxygen at room temperature is about 500 m s-1. The RMS speed of hydrogen at the same temperature is about