A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red-brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student ? Give reason for your answer.

Answer

No, the student's conclusion is wrong. The air from upper gas jar also diffuses down into the lower gas jar containing bromine vapour. But since air is colourless, it cannot be noticed by the student