Redox Reactions

• Oxidation can mean the addition of oxygen, and reduction can be the removal of oxygen
• A loss of electrons is called oxidation
• A gain of electrons is called reduction
• Reduction and oxydation happen at the same time - hence the term 'REDOX':

  • Iron atoms are oxidised to Fe2+ ions when they react with dilute acid: Fe + 2H+ -> Fe2+ + H2
  • The iron atoms lose electrons. They're oxidised by the hydrogen ions: Fe - 2e- -> Fe2+
  • The hydrogen ions gain electrons. They're reduced by the iron atoms: 2H+ + 2e- -> H2
• Displacement reactions are redox reactions
• Displacement reactions involve one metal kicking another one out of a compound. The rule is:

  • A more reactive metal will displace a less reactive metal from its compound
• If you put a reactive metal into the solution of a dissolved metal compound, the reactive metal will replace the less reactive metal in the compound
• If you put iron in a solution of copper sulfate (CuSO4) the more reactive iron will 'kick out' the less reactive copper from the solution. You end up with iron sulfate solution (FeSO4) and copper metal
• In this reaction the iron loses 2 electrons to become a 2+ ion - it's oxidised. The copper ion gains these 2 electrons to become a copper atom - its's reduced

  iron + copper sulfate -> iron sulfate + copper
• In displacement reactions, it's always the metal ion that gains electrons and is reduced. The metal atom always loses electrons and is oxidised
• In an ionic equation only the particles that react and the products they form are shown. E.g. Mg(s) + Zn2+(aq) -> Mg2+(aq) + Zn(s)

  This shows the displacement of zinc ions by magnesium metal
• The full equation of the displacement of zinc ions by magnesium metal is:

  Mg(s) + ZnCl2(aq) -> MgCl2(aq) + Zn(s)
• When ions in a reaction don't change the reaction they are called spectator ions
• Ionic equations for displacement reactions just concentrate on the substances which are oxidised or reduced