Chapter -10

• Redox reaction

  • Oxidation - loss of electrons, gain of oxygen
  • Reduction - gain of electrons, loss of oxygen
• Oxidation

  • Increase in oxidation state
• Reduction

  • Decrease in oxidation state
• Oxidation

  • Combustion: C + O₂ → CO₂
  • Respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
• Corrosion

  • Iron rusting: Fe + oxygen + water → iron oxide
  • Copper corrosion: Cu + oxygen + water → copper oxide (green)
• Rancid fat: fat + oxygen → rancid
• Oxidation

  Oxidized Al, reduced Fe
• Oxidizing agent - Fe³+, reducing agent - Al
• H₂O₂ is both an oxidizing and reducing agent
• KMnO₄ is an oxidizing agent, Fe²+ is a reducing agent
• Transition metals act as catalysts
• Oxidation numbers

  • Free state = 0
  • In compound: Group I = +1, Group II = +2, Oxygen = -2, Peroxide = -1, Hydrogen = +1, Metal hydride = -1
• Reduction

  Decrease in oxidation number
• Oxidation

  Increase in oxidation number
• Oxidized

  Reduced
• Oxidizing agent - Cl₂, reducing agent - KBr
• Combustion


  A chemical reaction in which a substance reacts with oxygen
• Exothermic reaction


  A chemical reaction in which heat energy is released to the surroundings
• Respiration


  A combustion reaction by which biological cells release the energy stored in glucose for use by the cell or the body
• Oxidation


  Gain of oxygen
• Reduction


  Loss of oxygen
• Redox


  Reactions involving simultaneous oxidation and reduction
• Corrosion


  The surface of reactive metal is attacked by air, water or other substances
• Rancid


  A term used to describe oxidised organic material (food) usually involving a bad smell
• Reducing agent


  A substance which reduces another substance during a redox reaction
• Oxidising agent


  A substance which oxidises another substance during a redox reaction
• Displacement reaction


  A reaction in which a more reactive element displaces a less reactive element from a solution of its salt
• Transition metals


  Elements from the central region of the Periodic Table
• Oxidation number


  A number given to show whether an element has been oxidised or reduced
• Oxidation is gain of oxygen, loss of electrons, and increase in oxidation number
• Reduction is loss of oxygen, gain of electrons, and decrease in oxidation number
• Redox reaction is a reaction involving simultaneous oxidation and reduction
• Reduction and Oxidation in terms of oxygen

  1. Lose oxygen: Reduction

  2. Gain oxygen: Oxidation
• Reduction


  • Fe,0, +3C0 L →2Fe+ 3CO,
• Oxidation


  • Fe2O3 loses oxygen (reduction)
  • CO gains oxygen (oxidation)
• Halogen displacement reaction


  1. Chlorine displaces iodine from potassium iodide solution

  2. Oxidation number of iodine changes from -1 to 0 (increased)

  3. Iodine ions are oxidised to iodine

  4. Oxidation number of chlorine changes from 0 to -1 (decreased)

  5. Chlorine is reduced to chloride ions