What is an oxidation-reduction reaction?

An oxidation–reduction reaction (redox reaction) is a type of chemical reaction in which there is a transfer of electrons between substances, leading to changes in their oxidation states.

Here’s the breakdown:

1. Oxidation
   • Loss of electrons.
   • The oxidation number of the element increases.
   • Example: Na → Na⁺ + e⁻
2. Reduction
   • Gain of electrons.
   • The oxidation number of the element decreases.
   • Example: Cl₂ + 2e⁻ → 2Cl⁻
3. Coupled Process
   • Oxidation and reduction always occur together: when one substance loses electrons (oxidized), another must gain those electrons (reduced).
4. Example of a Redox Reaction
   Reaction:
   2Na + Cl₂ → 2NaCl
   • Sodium (Na) is oxidized: Na → Na⁺ + e⁻
   • Chlorine (Cl₂) is reduced: Cl₂ + 2e⁻ → 2Cl⁻
5. Applications
   • Respiration (glucose oxidation in cells)
   • Combustion of fuels
   • Corrosion of metals (rusting of iron)
   • Electrochemical cells and batteries