Final answer:
The bromine gas will diffuse into the lower gas jar until its concentration is evenly spread out.
Step-by-step explanation:
Diffusion is the process by which molecules disperse in space in response to differences in concentration. In a closed environment, diffusion will ultimately result in equal concentrations of gas throughout. Therefore, in this case, the bromine gas will diffuse into the lower gas jar until its concentration is evenly spread out.