Question

With the help of a labeled diagram, describe a simple experiment to show the presence of oxygen and nitrogen in air using a piece of white phosphorus.

Answer 1

Activity to show the presence of oxygen and nitrogen in the air using a piece of white phosphorous

1. A trough is taken and filled with water

2. Over it is placed a bell-jar marked with five equal parts.

 

3. A crucible containing white phosphorus is placed on a cork

4. The cork is made to float on the water.

5. A heated iron rod is them taken.

6. The phosphorus is ignited with the heated rod.

Observations: 

Dense white fumes of phosphorus pentoxide (P₂O₅) are formed when the phosphorus (P) burns in the active component of air (oxygen).

The rise in the level of water in the bell-jar is by 1/5

Conclusion:

Oxygen (active compound)	1/5 (approx volume)	Supports combustion	Used up in burning
Nitrogen (In active component bell - jar)	4/5 (approx volume)	Does not support combustion	Remains behind in the combustion

The active component of air i.e. oxygen (1/5 of air) is used up in burning. The remaining inactive component of air i.e. nitrogen (4/ 5 of air) is not used up in burning.