ZIMSEC O Level Combined Science Notes:  The reduction process

  • Reduction is the opposite of oxidation
  • Reduction is the removal of oxygen from a substance/compound
  • It can also be the addition of oxygen
The reduction of copper. Image credit chemistrydemos.co.uk

The reduction of copper.

  • reducing agent removes oxygen or adds hydrogen
  • Metals cannot be yielded by heating their oxides
  • The metals have to be heated with a reducing agent
  • That will remove the oxygen from the oxide to yield the metal
  • The metal oxide is reduced into a metal
  • The reducing agent that can be used can be any of the following:
  • a metal that is higher up in the reactivity series when compared to the metal being extracted
  • hydrogen
  • or it could be carbon
  • All these can act as reducing agent
  • For example:
  • \text{copper oxide+hydrogen}\rightarrow\text{copper+water}
  • Hydrogen can be used to remove (displace)  oxygen from a compound
  • Carbon can also be used to reduce copper oxide yielding the copper
  • The equation can be written as:
  • \text{copper oxide+carbon}\rightarrow\text{copper+carbon dioxide}
  • A metal that is higher up in the reactivity series can be used to reduce a metal that is lower in the reactivity series
  • This is because the more reactive has a higher affinity for oxygen when compared to the metal that is lower in the series
  • The more reactive metal will thus “take” oxygen from the less reactive metal
  • The more reactive metal displaces the less reactive metal
  • This leaves the less reactive metal and an oxide of the more reactive metal
  • For example:
  • \text{iron oxide+aluminium}\rightarrow\text{iron+aluminium dioxide}
  • Aluminum is higher up in the reactivity series when compared to iron
  • The aluminum reduces the iron (III)  oxide to leave iron and aluminum oxide
  • A lot of heat is given out in the reaction
  • Exothermic reactions give out heat

To access more topics go to the Combined Science Notes page.


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