Why a leaking ballon filled with H2 placed in container will experienced more pressure?

Question

Why a leaking ballon filled with H2 placed in container will experienced more pressure?

Answer 1

Because the surrunding area will not be air. it will have H2 and air mix in the container. That will make the density of surrounding air smaller. it is like putting it in a vacuum. it will have more presure for the ballon from inside to the out.