Separation of the Gases of the Air
Air is a mixture of gases like nitrogen, oxygen, argon, carbon dioxide, helium, neon, krypton, and xenon, etc. The major component of air is nitrogen (78.03%). The second major component of air is oxygen (20.99%), and the third major component of air is argon (0.93%). All the remaining gases of air constitute only 0.05% of air. Nitrogen is used for making fertilisers. Oxygen is used for making steel in factories, and in hospitals (to help patients having breathing difficulties). Argon is filled in electric bulbs. All these gases are obtained from air on a large scale. This is because air is the cheapest source of these gases.
The various gases of air are separated from one another by the fractional distillation of liquid air. This separation is based on the fact that
the different gases of air have different boiling points (when in liquid form).The boiling points of the three major gases of air, nitrogen, oxygen and argon, are given below :
| Gas | Boiling point
(of liquefied gas) |
Nitrogen -196&de;C
Argon -186&de;C
Oxygen -183&de;C | Lowest Boiling point
Highest boiling point |
Liquid air is an extremely cold liquid. Liquid air contains all the component gases in the liquid form. When liquid air is warmed gradually during fractional distillation, the various liquefied gases present in it boil off at different temperatures (according to their boiling points) and collected separately at different heights in the fractional distillation column. We will now describe how gaseous air is converted into liquid air, and how the three major components, nitrogen, oxygen and argon, are separated from it.
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Matter in Our Surroundings - Notes
1. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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3. The Case of a Liquid Solute Dissolved in a Liquid Solvent
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4. 11. Metals Usually Have a Silver or Grey Colour
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7. Separation Of Mixture Of a Solid And a Liquids
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10. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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11. To Study the Properties of a Colloid
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13. 6. Non-Metals are Not Strong. They Have Low Tensile Strength.
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17. 1. Separation by a Suitable Solvent
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20. 11. Non-Metals Have Many Different Colours.
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21. To Study the Properties of a Compound of Iron and Sulphur
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22. 6. Metals are Usually Strong. They Have High Tensile Strength.
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26. To Study the Properties of a Solution
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32. 3. Metals are Good Conductors of Heat and Electricity.
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33. Separation of Mixture Of Two Solids
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37. To Study the Properties of a Suspension
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38. Chemical Formula for daily use material
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42. To Separate a Mixture of Alcohol and Water
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49. To Separate the Salt-Water Mixture (or Salt-Solution)
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50. 1. Separation by Fractional Distillation
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