About Chemistry

1)It's because when we absorb oxygen and exhaust CO2, the plants absorb CO2 to carry out photosynthesis and produce oxygen. The amount of oxygen produced is same to the amount of CO2 absorbed of the plant.

2)In industry, we carry out fractional distillation to separate nitrogen and oxygen from air. Fractional distillation make use of the difference of boiling point between nitrogen and oxygen.

Using fractional distillation for separating nitrogen and oxygen from air:

1.We first remove the dust, CO2 and water vapour from the air.

2.Cool and compress the purified air and then pass it through ajet into an expansion chamber. It will expand quickly and its temperature will drop sharply. The compressing and expanding cycle is repeated until its temperature reaches -200 degree Celsius.

3.Pump the liquid air into a frationating column, allow it to warm up slowly, the nitrogen in the liquid air will become gas first since the boiling point of nitrogen is lower than the boiling point of oxygen, the nitrogen gas is collected at the top of the column. Then, the oxygen becomes gas and collected from the lower part of the column.