9.1. Hydrogen, Oxygen and ozone : 4 teaching hours

Unit 9.1: Hydrogen, Oxygen, and Ozone (4 Teaching Hours)

1. Hydrogen

   • Chemistry of Atomic and Nascent Hydrogen
     • Atomic Hydrogen: Formed by dissociating H₂ molecules into H atoms under high energy (e.g., electric arc). Highly reactive due to unpaired electrons.
     • Nascent Hydrogen: Freshly formed H atoms during reactions (e.g., Zn + H₂SO₄ → ZnSO₄ + 2H). More reactive than H₂, reduces compounds like KMnO₄.
   • Isotopes of Hydrogen and Their Uses
     • Protium (¹H): Most abundant (99.98%), used in NMR spectroscopy.
     • Deuterium (²H or D): Used in deuterated solvents, heavy water (D₂O), and nuclear reactors.
     • Tritium (³H): Radioactive, used in nuclear fusion, self-powered lighting, and tracers.

                     Figure 1: Structure of Hydrogen Isotopes (Diagram showing ¹H, ²H, ³H nuclear composition).

1. • Application of Hydrogen as Fuel
     • High energy content (120–142 MJ/kg), eco-friendly (produces H₂O).
     • Used in fuel cells for electricity (e.g., electric vehicles).
     • Challenges: Storage and production costs.
   • Heavy Water (D₂O) and Its Applications
     • Contains deuterium instead of protium.
     • Applications: Nuclear reactor moderator, NMR spectroscopy, biochemical tracers.

2. Oxygen

   • Allotropes of Oxygen
     • Allotropy: Element existing in multiple forms with different properties.
     • Dioxygen (O₂): Most common, stable gas.
     • Ozone (O₃): Triatomic, protects from UV radiation.
     • 
       
     • Figure 2: Structure of Dioxygen and Ozone (Diagram showing O₂ and O₃ molecular structures).
   • Types of Oxides
     • Acidic Oxides: Non-metal oxides (e.g., CO₂, SO₂) form acids with water.
     • Basic Oxides: Metal oxides (e.g., Na₂O, CaO) react with acids.
     • Neutral Oxides: No reaction with acids/bases (e.g., CO, N₂O).
     • Amphoteric Oxides: Act as acidic and basic (e.g., Al₂O₃, ZnO).
     • Peroxides: Contain O₂²⁻ (e.g., H₂O₂, Na₂O₂).
     • Mixed Oxides: Multiple oxidation states (e.g., Fe₃O₄, Pb₃O₄).
   • Applications of Hydrogen Peroxide (H₂O₂)
     • Bleaching (textiles, paper, hair).
     • Disinfectant/antiseptic in medical use.
     • Oxidizing agent in chemical synthesis, wastewater treatment.
   • Medical and Industrial Applications of Oxygen
     • Medical: Oxygen therapy, anesthesia, hyperbaric chambers.
     • Industrial: Steel production, welding, chemical synthesis, rocket propulsion.

3. Ozone

   • Occurrence
     • Found in stratosphere (15–35 km), formed by UV splitting O₂.
   • Preparation of Ozone from Oxygen
     • Pass dry O₂ through silent electric discharge: 3O₂ → 2O₃ (endothermic).
   • Structure of Ozone
     • Triatomic, bent molecule (116.8° bond angle), resonance hybrid.
     • 
       
     • Figure 3: Resonance Structures of Ozone (Diagram showing resonance forms).
   • Test for Ozone
     • Turns starch iodide paper blue (liberates I₂).
     • Reduces KMnO₄ solution.
   • Ozone Layer Depletion
     • Causes: CFCs, halons release Cl atoms, catalyzing O₃ breakdown.
     • Effects: Increased UV radiation, skin cancer, ecosystem damage.
     • Control Measures: Montreal Protocol (1987), HFC alternatives, awareness.
   • Uses of Ozone
     • Water/air purification, bleaching, medical sterilization.