Chapter 12 Oxidation and Reduction

• Gain and Loss of oxygen

  • oxidation is the gain of oxygen
  • reduction is the loss of oxygen
• Gain and Loss of hydrogen

  • oxidation is the loss of hydrogen
  • reduction is the gain of hydrogen
• Gain and Loss of electrons

  • oxidation is the loss of electrons
  • reduction is the gain of electrons
• Oxidation State


  • the oxidation state is the charge of an atom of an element would have if the atom exists as an ion in a substance
  • e.g. +1, -2
• Redox

  • when reduction and oxidation take place at the same time in a reaction
  • Answering technique : what is oxidised, what is reduced, since both oxidation and reduction take place at the same time, it is a redox reaction
• Oxidising agent

  • a substance that oxidises other reactants in the same reaction, with it itself being reduced
  • aqueous potassium iodide is used to test for oxidising agents, if the unknown solution is an oxidising agents, it will turn colourless potassium iodide solution yellow-brown
  • If the unknown gas is an oxidising agent it will turn white potassium iodide starch paper blue
• Reducing agent

  • a substance that reduces other reactants in the same reaction with it itself being oxidised
  • acidified potassium manganate (VII) solution is used to test for reducing agents. If the unknown solution is a reducing agent, purple acidified potassium manganate (VII) will turn colourless
  • if the unknown gas is a reducing agent, purple acidified potassium manganate (VII) solution in the strip of filter paper turns colourless\