Metal ores
Ores are naturally occurring rocks that contain metals or metal compounds in sufficient amounts to make it worthwhile extracting them. The method used to extract a given metal from its ore depends upon the reactivity of the metal and so how stable the ore is.
In each case, the metal ion in the compound gains electrons, ie they are reduced.
Ores of very reactive metals have to be melted and electrolysed with a DC (direct current) supply of electricity.
The positive metal ions are attracted to the negative electrode where they accept electrons.
For example:
\(Na_{}^ + (aq) + e_{}^ - \to Na(s)\)
(sodium ions + electrons → sodium metal)
Ores of reactive metals have to be heated with carbon or carbon monoxide in order to extract the metal.
For example:
\(2Cu_{}^{2 + }O_{}^{2 - }(s) + C(s) \to 2Cu(s) + CO_2^{}(g)\)
(copper ions + carbon → copper metal + carbon dioxide)
When ores of reactive metals such as copper are heated with carbon or carbon monoxide, they are being reduced. Since it is the presence of carbon or carbon monoxide that causes the reduction to take place, we can refer to these chemicals as reducing agents.
Ores of unreactive metals only need to be heated to obtain the metal.
For example:
\(2Ag_2^ + O_{}^{2 - }(s) \to 4Ag(s) + O_2^{}(g)\)
(silver ions → silver metal + oxygen)