Question

Demonstrate through a simple experiment that the air mainly contains nitrogen and oxygen in the volume ration of $4:1$.

Answer 1

Aim of experiment: To show that air contains nitrogen and oxygen in the ratio $4:1$ by volume.
Procedure: Take a glass container and fix a candle at its center. Put some quantity of water in the container. Place an empty, dry gas jar over it. Mark five marks above water surface on the jar at equal distances shown in the figure given below.
The candle is lightened and is covered with the gas jar. After some time the candle is extinguished and the water level is raised in gas jar. The raised level in water is $1/5$ of the volume of air in the gas jar.
This proves that one part of the air of the jar is a gas which supports combustion, i.e., oxygen. Hence, $1/5$ by volume is oxygen in air.