Gas Diffusion Leads to Uniform Mixing

Steps:

• Initially, brown gas occupies one half and colourless gas the other, separated by the wall.
• Removing the wall allows molecules of both gases to move randomly via diffusion.
• Over a long time, diffusion continues until gas molecules are evenly distributed throughout the box.
• The non-reacting gases form a homogeneous mixture, diluting the brown gas to pale brown everywhere.

Why B is correct:

• Diffusion, as per kinetic molecular theory, causes gases to mix uniformly until concentrations equalize, resulting in pale brown gas throughout.

Why the others are wrong:

• A: Gases diffuse and mix, preventing separation by side.
• C: Diffusion eliminates distinct clouds, creating a uniform mixture.
• D: Initial positions reverse due to mixing, not separation.

Final answer: B