I did not understand this.
Aim: to show that air contain oxygen and nitrogen.
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Theory:
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Dear Student, Experiment for the presence of nitrogen in air : 1)Air smpling pump is used to bubble the atmospheric gas through nitrogen dioxide absorbing agent(10 ml). 2) This sample with absorbed Atmospheric gas is treated with nitrogen dioxide reagents 3) Color change in the sample after treatment with the reagent shows the presence of nitorgen gas in atmosphere. Take a glass vessel and fix a candle at its centre. Now, fill half the glass vessel with water and place an inverted gas jar over the candle. Note the water level. Remove the gas jar and light the candle, and again cover it with the former. After some time, the candle will extinguish and the level of water in the gas jar will rise up. As all the oxygen in the jar was consumed, the candle stopped burning, and the place occupied by this gas became empty, thereby raising the level of water in the jar. Now, remove the gas jar by keeping its mouth tightly closed, and introduce a burning splinter into it. The splinter will get extinguished. This shows that the remaining air in the jar does not support burning. This gas is nitrogen. This activity proves that air contains oxygen and nitrogen. Experiment for the presence of Oxygen: We all know oxygen helps in combustion and thus if oxygen is not present in atmosphere then burning will not take place. Regards