14. Redox

Oxidation
  • The gain in oxygen or the loss of hydrogen
  • The increase in oxidation state
  • The loss of electrons of a substance in a chemical reaction.

Reduction
  • The loss in oxygen or the gain of hydrogen
  • The decrease in oxidation state
  • The gain of electrons of a substance in a chemical reaction.

Redox Reactions
  • A redox reaction refers to both oxidation and reduction occurring in the same chemical reaction simultaneously.
  • Types of redox reactions
  1. Metal + Dilute acids
  2. All combustion reactions
  3. Displacement reaction    
  4. Extraction of less reactive metals using Blast furnace.

  • Typical non- redox reactions:
    1. Neutralization
    2. Precipitation
    3. Thermal decomposition of carbonates

Oxidising and Reducing Agents
  • When a substance is reduced, it acts as an oxidising agent. Acidified potassium dichromate(VI) turns from orange to green. Acidified potassium manganate(VII) turns from purple to colourless.
  • When a substance is oxidised, it acts as a reducing agent. Potassium iodide turns from colourless to brown. Hydrogen peroxide produces oxygen.