Air | Jamb Chemistry

Natural Constituents of Air and Their Proportions

1. Definition of Air: A mixture of gases that forms the Earth’s atmosphere.
2. Composition of Air:
   • Nitrogen $(N_2)$: ~78%
   • Oxygen $(O_2)$: ~21%
   • Argon $(Ar)$: ~0.93%
   • Carbon Dioxide $(CO_2)$: ~0.04%
   • Water Vapor: Varies, usually 0.1–4%.
3. Trace Gases: Include neon $(Ne)$, helium $(He)$, methane $(CH_4)$, krypton $(Kr)$, and hydrogen $(H_2)$.
4. Nitrogen $(N_2)$:
   • Largest constituent.
   • Chemically inert under normal conditions.
5. Oxygen $(O_2)$:
   • Vital for respiration and combustion.
   • High reactivity allows it to form oxides.
6. Argon $(Ar)$:
   • Inert noble gas.
   • Used in welding and lighting.
7. Carbon Dioxide $(CO_2)$:
   • Essential for photosynthesis.
   • Contributes to the greenhouse effect.
8. Water Vapor:
   • Regulates temperature.
   • Essential for weather patterns and precipitation.
9. Neon $(Ne)$:
   • Inert gas used in neon lighting.
10. Mixture Nature: Air is not a compound but a physical mixture of gases with no fixed chemical bonds.
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Air as a Mixture and Reasons for Its Existence as a Mixture

11. Reason for Mixture: Gases in the air retain their individual properties and do not chemically bond.
12. Physical Mixture: The components are separable by physical means, such as fractional distillation.
13. Homogeneity: Air appears uniform but is composed of different gases in specific ratios.
14. Diffusion: Gases mix due to diffusion, distributing evenly in the atmosphere.
15. Non-reactivity: Noble gases and nitrogen maintain air's stability by reducing reactivity.
16. Atmospheric Layers: Proportions of gases vary with altitude; oxygen decreases, and helium increases in the upper atmosphere.
17. Dynamic Nature: Water vapor content changes with temperature and humidity.
18. Retention of Properties: Each gas in air retains its unique characteristics, such as oxygen's reactivity or argon's inertness.
19. Physical States: Air components exist in the gaseous state under standard conditions.
20. Industrial Importance: The separation of air components provides resources for industries and medical applications.
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Uses of Air Constituents

Oxygen O_2

25. Respiration: Essential for the survival of aerobic organisms.
26. Medical Applications: Used in oxygen therapy and life-support systems.
27. Combustion: Supports burning in industrial and domestic settings.
28. Steelmaking: Used to remove impurities during steel production.
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Argon Ar

29. Welding: Provides an inert atmosphere for arc welding.
30. Lighting: Used in fluorescent and incandescent light bulbs.
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Carbon Dioxide CO_2

31. Photosynthesis: Critical for plant life, converting $CO_2$ into glucose.
32. Carbonation: Adds fizz to beverages.
33. Fire Extinguishers: Non-flammable gas used to smother flames.
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Neon Ne

34. Neon Lighting: Produces bright red-orange light in advertising signs.
35. High-Voltage Indicators: Neon glows when exposed to electric discharge.
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Separation of Air Components

36. Principle: Components are separated based on differences in boiling points.
37. Fractional Distillation: A common method for separating air into its components.
38. Process Steps:
    • Air is compressed and cooled to a liquid state.
    • Gradual heating separates gases as they boil at different temperatures.
39. Boiling Points:
    • $N_2$: -196°C
    • $O_2$: -183°C
    • $Ar$: -186°C
40. Cryogenic Air Separation: Utilizes extremely low temperatures to liquefy air.
41. Adsorption Methods: Molecules adhere to surfaces to separate gases like $CO_2$.
42. Gas Permeation: Membranes separate air based on molecule size.
43. Applications of Separation:
    • Medical oxygen production.
    • Nitrogen for preserving food.
44. Industrial Equipment: Air separation units (ASUs) are used in large-scale operations.
45. Environmental Importance: Enables the capture of industrial $CO_2$ emissions.
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Properties and Applications of Air Constituents

46. Density Variations: Lighter gases like $H_2$ and helium rise to the upper atmosphere.
47. Role in Life Support: Oxygen sustains life, while nitrogen maintains atmospheric pressure.
48. Weather Influence: Water vapor regulates temperature and drives the water cycle.
49. Energy Uses: Combustion of oxygen fuels engines and power plants.
50. Scientific Research: Noble gases are used in experiments and advanced technologies.

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