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At constant volume the temperature of a gas is increased. Then

Asked in CBSE AIPMT 1989 · Origin of pressure and wall impacts

Answer: (2) the number of collisions per unit time will increase

Step-by-step solution

Given: a fixed volume, with the temperature raised.

Idea: the rate at which molecules strike the walls is set by their speed, and their speed is set by the temperature.

Mean speed: v∝√T, so heating speeds the molecules up.

The volume and the number of molecules are unchanged, so the number density is unchanged.

Collision rate with the walls ∝ nv, and only v has changed.

So the number of wall collisions per unit time increases.

This is also why the pressure rises: each impact is harder and there are more of them.

Why the other options are wrong

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