Friday, July 1, 2011

Chemistry Form 5: Chapter 3 - Rusting of Iron

  • Rusting is a corrosion of iron.
  • For iron to rust, oxygen and water must be present.
  • In the presence of acids and salts, rusting occurs faster because these substances increase the electrical conductivity of water, making water a better electrolyte. 
  • Oxygen acts as the oxidizing agent and iron acts as the reducing agent.

·     The surface of iron at the middle of the water droplet serves as the anode at which oxidation occurs. The iron atoms lose electrons to form iron (II) ions.

·     The electrons flow to the edge of the water droplet where there is plenty of dissolved oxygen. The iron surface there serves as cathode at which reduction occurs. Oxygen gains the electrons and is reduced to hydroxide ions.

·     The iron (II) ions produced combine with the hydroxide ions to iron (II) hydroxide. The Fe(OH)2 is then further oxidized by oxygen to form iron (III) oxide, Fe2O3 known as rust

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