In a cubical vessel are enclosed n molecules of a gas each having a mass m and an average speed v . If l is the length of each edge of the cube, the pressure exerted by the gas will be

Change in momentum will be Δp=2mvxTime of collision between two walls=Δt=2 ℓvxForce by all molecules acting on wall=F=ΔpΔt=nmvx2ℓDue to randomness in all three directions,vx2=v23∴F=mnv23ℓSo, presssure on wall=FA=mnv23ℓ3