Question

a gas exerts pressure on the walls of the container,why?

Answer 1

The simple answer to your question would be that gas exerts pressure on the container in which it is contained becausethe molecules of the gas are constantly colliding with thecontainer, and exerting pressure. This is because they have energy and are constantly moving.

Answer 2

Because in the gaseous state, the particles move about randomly at high speed. Due to this random movement, the particles hit each other and also the walls of the container. The pressure exerted by the gas is because of this force exerted by gas particles per unit area on the walls of the container.