Question

When a gas jar full of air is placed upside down on a gas jar full of bromine vapours, the red-brown vapours of bromine from the lower jar go upward into the jar containing air. In this experiment
(A) bromine cannot be heavier than air because it is going upwards against the gravity
(B) both air and bromine have the same density, the air is heavier than bromine
(C) bromine is heavier than air
(D) air is heavier than bromine

Answer 1

Hint: The process that is involved in this situation is known as diffusion and diffusion will be in respect to kinetic energy. The kinetic energy of bromine is very high as compared to air. The heavier element will settle down in the bottom and the lighter one will rise above it.

Complete step by step solution:
From your chemistry lessons you have learned about the diffusion process and how it takes place.
Diffusion is a process in which mixing of substances takes place due to the motion of particles. In the given situation a diffusion process takes place.
From the question we can see when a gas jar full of air is placed upside down on a gas jar full of bromine vapours, the red-brown vapours of bromine from the lower jar go upward into the jar containing air this happens because the particle of bromine in a lower jar and the particle of air is upper jar both are in a gaseous state and have a random motion.
Bromine gas is heavier than air due to its atomic weight. Being heavier it still floats in the air due to diffusion and collision between the particles of bromine and air molecules. The particles collide with each other, so the two different gases can mix completely with each other.
As we know that gas has maximum kinetic energy and they can move with high speed in any direction and exert pressure on the wall of the container.
The particles of air and bromine vapour collide with each other and spread in all the directions of the jar and they get uniformly mixed and thus after some time the jar in which air is present also gets a red-brown colour and this process is known as diffusion.

Thus the correct option will be (C).

Note: Kinetic energy of bromine is very high as compared to air and thus it tends to move upward and mix with air. Bromine is heavier than air and thus it will settle down in the bottom of the jar and air will rise at the top of the jar. Due to diffusion of particles the whole jar will appear as reddish-brown after the collision of particles.