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Kinetic Theory Of Gases Assumptions MCQ - Practice Questions with Answers

Edited By admin | Updated on Sep 25, 2023 25:23 PM | #NEET

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4 Questions around this concept.

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There are two identical chambers, completely thermally insulated from the surroundings. Both chambers have a partition wall dividing the chambers into two compartments. Compartment 1 is filled with an ideal gas and compartment 3 is filled with a real gas. Compartments 2 and 4 are vacuum. A small hole (orifice) is made in the partition walls and the gases are allowed to expand in a vacuum.

Statement 1: No change in the temperature of the gas takes place when the ideal gas expands in a vacuum. However, the temperature of real gas goes down (cooling) when it expands in a vacuum.

Statement 2: The internal energy of an ideal gas is only kinetic. The internal energy of a real gas is kinetic as well as potential.

Statement 1 is false and statement 2 is true

Statement 1 and statement 2 both are true statement 2 is the correct explation of statement 1.

Statement 1 is true and statement 2 is false.

Statement 1 and statement 2 both are true. But statement 2 is not the correct explation of statement 1.

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The volume occupied by the molecules contained in $4.5 Kg$ water at $STP,$ if the intermolecular forces vanish away is -

$5.6 \times 10^6 \mathrm{~m}^3$

$5.6 \times 10^3 \mathrm{~m}^3$

$5.6 \mathrm{~m}^3$

$5.6 \times 10^-^3 \mathrm{~m}^3$

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Concepts Covered - 1

Assumption of ideal gases

Ideal gas - It is a hypothetical gas (which is not real gas), whose molecules occupy negligible space and have no interactions (Force of interaction is very less), and which consequently obeys the gas laws exactly.

So, the ideal gas does not exist in real, but for study we take some assumption to make the gas ideal and we can apply some laws which are only valid for ideal gases. These assumptions are -

The size of the molecules is negligible in comparison to intermolecular distance ( $10^{-9} m$ ).
The molecules of a gas are identical, spherical, rigid and perfectly elastic point masses (It means that when they collide with each other, then there is no loss of energy while collision).
The molecules of a given gas are all identical but these molecules are different than those of another gas.
The volume of molecules is negligible in comparison to the volume of gas.
Molecules of a gas moves randomly in all possible direction with all possible velocities.
The speed of gas molecules varies from zero and infinity.
The gas molecules keep on colliding among themselves as well as with the walls of containing vessel. These collisions are perfectly elastic (no loss of energy).
The time spent in a collision between two molecules is negligible in comparison to time between two successive collisions (i.e., time required to travel mean free path).
The number of collisions per unit volume in a gas remains constant.
No attractive or repulsive force acts between gas molecules.
Gravitational attraction among the molecules is negligible due to extremely small masses and very high speed of molecules.
Molecules constantly collide with the walls of container due to which their momentum changes. The change in momentum is transferred to the walls of the container and due to this Pressure is exerted by gas molecules on the walls of container.
The density of gas does not changes at any point of container.