Can the vessel be filled with gas up to 70%. Why?

One of the properties of a gas is to completely fill the volume of the vessel in which it is enclosed. It is impossible to fill the vessel with gas so that gas is concentrated in one part of it, and the other remains absolutely empty. Even if we imagine that at some initial moment of time it was possible to achieve this by some tricks, then after a very short period of time the gas molecules will fill all the available space. They are not connected with each other, have high speeds, randomly collide with each other and constantly change the direction of flight, falling into that part of the vessel where they just were not.