# What are some examples of reduction reactions?

May 13, 2014

Reduction can be considered as the removal of oxygen, the addition of hydrogen, or the gain of electrons.

Removal of oxygen:
Metal ores which are oxides are reduced to the metal - this is how iron is made from iron ore. The reducing agent is carbon monoxide.
$F {e}_{2} {O}_{3}$ + $3 C O$ --> $2 F e$ + $3 C {O}_{2}$

Aldehydes and ketones can be reduced to primary or secondary alcohols respectively using aqueous sodium borohydride. This is a source of ${H}^{-}$ ions which bring about the reduction:
$C {H}_{3} C H O$ + $2 \left[H\right]$ --> $C {H}_{3} C {H}_{2} O H$

Copper oxide can be reduced to copper by heating it while passing hydrogen gas over it. The hydrogen gets oxidised to form water.
$C u O$ + ${H}_{2}$ --> $C u$ + ${H}_{2} O$

Gain of electrons:
The formation of non-metal ions from the corresponding element, for example during electrolysis, is an example of this, e.g.
$C {l}_{2}$ + $2 {e}^{-}$ --> $2 C {l}^{-}$

In the same way, positive metal ions can gain electrons to be reduced to the metallic element:
$C {u}^{2 +}$ + $2 {e}^{-}$ --> $C u$