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Experiment: determination of the active part of air.

Answer Text:
Experiments:
Determination of the active part of air.
1. Burning candle in air.
Apparatus and requirements.
- Candle;
- Cork / evaporating dish;
- Sodium hydroxide
solution;
Procedure:
- A candle about 3cm long is put on a wide cork/ evaporating dish;
- It is then floated in a dilute solution of sodium hydroxide solution just above the beehive shelf;
- It is carefully covered with a dry #100cm^3# measuring cylinder, during which the level of solution in the cylinder is noted and marked;
- The measuring cylinder is removed and the candle lit;
- The lighting candle is then covered with a measuring cylinder;
- The experiment is allowed to proceed until the candle goes off;
Observations:
- The candle went off after sometime;
- The sodium hydroxide level inside the gas jar rises;
- The sodium hydroxide level in the trough goes down;
Diagrams:

Explanations:
- The candle wax is made up of hydrogen and carbon, hence called a hydrocarbon;
- During burning it melts in air consuming oxygen and producing carbon (IV) oxide and water vapour;
- The water vapour condenses giving a negligible volume of water;
- The resultant carbon (IV) oxide is absorbed by the sodium hydroxide;
- Absorption of carbon (IV) oxide in the gas jar creates a partial vacuum within it;
- The sodium hydroxide in the trough rises to fill the resultant space; and hence adrop in the sodium hydroxide level in the tough;
Conclusion.
- Oxygen is the active part of air that is utilized during burning;
- Air is basically made up of
2 parts; an active part that supports burning and an inactive part that does not support burning;