Nitrogen (N)

• General Information:
  • Group: V
  • Period: 2
  • Atomic Number: 7
  • Electron Configuration: 2.5
  • Valency: 3 (also exhibits 5)
  • Makes up approximately 78% of air.
• Sources:
  • Air (atmosphere)
  • Earth’s crust
  • Lightning
  • Proteins
  • Amino acids
  • Leguminous plants (e.g., groundnuts, pigeon peas)
  • Fertilizers (e.g., ammonium nitrate, ammonium phosphate, sodium nitrate)
• Physical Properties:
  • Colorless
  • Odorless
  • Insoluble in water
  • Less dense than air
• Chemical Properties:
  • Diatomic gas (N₂) with strong triple covalent bonds.
  • Inert under normal conditions; reactive at high temperatures.
• Reactions:
  • With alkali metals:
    6K+N2→2K3N
  • With alkaline earth metals:
    3Mg+N2→Mg3N2
  • With hydrogen (reversible reaction):
    N2+3H2⇌2NH3
• Uses:
  • Production of ammonia
  • Food preservation
  • Fire prevention in oil tankers
  • Refrigerant (liquid nitrogen)
  • Shrink-fitting machine parts

Uses of Nitrogen

• Providing an Inert Atmosphere:
  • Chemical Reactions: Nitrogen is used to create an inert atmosphere in chemical processes to prevent unwanted reactions, particularly oxidation.
  • Storage: It helps preserve sensitive materials and chemicals by displacing oxygen, thus extending shelf life.
• As a Coolant:
  • Cryogenic Applications: Liquid nitrogen is used as a coolant in various applications, including:
    • Cryopreservation: Preserving biological samples (e.g., sperm, eggs, and cells) at extremely low temperatures.
    • Industrial Processes: Cooling and freezing food products quickly, enhancing quality and extending shelf life.
• Food Packaging:
  • Modified Atmosphere Packaging (MAP): Nitrogen is used in food packaging to replace oxygen, which helps:
    • Prevent Spoilage: Reducing oxidation and bacterial growth, thereby maintaining freshness.
    • Enhance Shelf Life: Extending the storage time of perishable products like fruits, vegetables, and meats.

Isolation of Nitrogen from Air

Nitrogen can be isolated from the air using several methods, but the most common and efficient method is fractional distillation. Here’s a step-by-step explanation of how this process works:

1. Fractional Distillation

Air Collection:

• Compression: The process begins by collecting air from the atmosphere. The air is then compressed to increase its pressure.
• Cooling: After compression, the air is cooled to very low temperatures. This cooling causes the air to change from a gas to a liquid, resulting in liquid air.

Separation:

• Heating: The liquid air is transferred to a fractionating column, where it is gradually heated. As the temperature rises, the different gases in the air start to evaporate at their respective boiling points.
• Boiling Points:
  • Nitrogen has a boiling point of -196°C, which is lower than that of oxygen.
  • Oxygen, with a boiling point of -183°C, remains in the liquid state longer than nitrogen.

Collection:

• As the nitrogen vaporizes, it rises up the fractionating column and is collected as a gas.
• This nitrogen gas can be further purified if needed to remove any impurities or other gases that may have been collected during the process.

• Compounds:
  • Ammonia (NH₃)
  • Nitric acid (HNO₃)
  • Nitrogen oxides (NO, NO₂)
• Preparation of Ammonia: Ca(OH)2+NH4Cl→CaCl2+H2O+NH3

Ammonia (NH₃)

Properties of Ammonia:

• Colorless, pungent smell
• Very soluble in water
• Basic (turns red litmus blue)
• Forms white smoke with HCl: NH3+HCl→NH4Cl

• Uses of Ammonia:
  • Making nitric acid
  • Manufacturing plastics and fertilizers
  • Softening hard water
  • Used in dry cells and explosives

Preparation of Ammonia Using the Haber Process

The Haber Process is a method used to synthesize ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) gases under high temperature and pressure.

Steps of the Haber Process

1. Reactants:

   • Nitrogen gas (N₂) is obtained from the air.

   • Hydrogen gas (H₂) is usually derived from natural gas (methane, CH₄) through steam reforming.

2. Chemical Reaction:
   N2(g)+3H2(g)⇌2NH3(g)

3. Conditions:

   • Temperature: Approximately 450°C.

   • Pressure: About 200 atmospheres.

   • Catalyst: Iron catalyst to increase the reaction rate.

4. Process:

   • The gases are mixed and passed over the catalyst at high temperature and pressure.

   • Ammonia is produced and can be liquefied and collected.

5. Recycling:

   • Unreacted nitrogen and hydrogen gases are recycled back into the system to improve efficiency.

Nitric acid (HNO₃)

• Preparation of Nitric Acid: KNO3+H2SO4→KHSO4+HNO3
• Uses of Nitric Acid:
  • Nitrate fertilizers
  • Explosives (TNT, dynamite)
  • Metal purification
  • Manufacturing dyes and drugs

Preparation of Nitric Acid Using the Ostwald Process

The Ostwald Process is used to produce nitric acid (HNO₃) from ammonia (NH₃) through a series of steps.

Steps of the Ostwald Process

1. Starting Material:

   • Ammonia (NH₃), usually produced by the Haber Process.

2. Step 1: Oxidation of Ammonia:

   • Ammonia is oxidized to form nitrogen monoxide (NO).

3. Chemical Reaction:
   4NH3(g)+5O2(g)→4NO(g)+6H2O(g)

   • This reaction occurs at high temperatures (about 900°C) in the presence of a platinum or rhodium catalyst.

4. Step 2: Oxidation of Nitrogen Monoxide:

   • Nitrogen monoxide (NO) is further oxidized to form nitrogen dioxide (NO₂).

5. Chemical Reaction:
   2NO(g)+O2(g)→2NO2(g)

6. Step 3: Formation of Nitric Acid:

   • Nitrogen dioxide (NO₂) is absorbed in water to produce nitric acid.

7. Chemical Reaction:
   3NO2(g)+H2O(l)→2HNO3(aq)+HNO(g)

8. Result:

   • The final product is nitric acid, which can be concentrated and used in various applications.