On the basis of kinetic theory of gases, the gas exerts pressure because its molecules :

suffer change in momentum when impinge on the walls of container.

continuously lose their energy till it reaches wall.

are attracted by the walls of container.

continuously stick to the walls of container.

Heat and Thermodynamics PYQ — JEE Main 2021 · 24 Feb · Shift 2 · Q55 with Solution

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Correct answer: C

Idea from kinetic theory of gases

In kinetic theory, gas molecules are in continuous random motion. They keep colliding with one another and with the walls of the container.
Why pressure is produced

When a molecule strikes the wall, its velocity component perpendicular to the wall changes direction.

If a molecule of mass $m$ hits a wall with perpendicular velocity component $v_x$ , then after elastic collision it becomes $-v_x$ .

So the change in momentum of the molecule is
$\Delta p = (-mv_x) - (mv_x) = -2mv_x$
Hence, the wall experiences an equal and opposite impulse.
Connection with pressure

Pressure is defined as force per unit area:
$P = \frac{F}{A}$
The force on the wall arises from the rate of change of momentum due to repeated molecular collisions.

Therefore, gas exerts pressure because molecules suffer change in momentum when they impinge on the walls.
Checking the options
- A: Incorrect. Molecules do not continuously lose all their energy till they reach the wall.
- B: Incorrect. Pressure is not due to attraction by the walls.
- C: Correct. Pressure is due to change in momentum during collisions with the walls.
- D: Incorrect. Molecules do not continuously stick to the walls.
Final answer

The correct option is C.