CHEM question

To extract a metal from its ore, the method depend on the reactivity of the metal.

For the metals with high reactivity (e.g. K, Na, Ca, Mg, Al, etc):
The method used is to electrolyze the molten liquid of the oxide or chloride of the metal.
For example, electrolyze the molten liquid of NaCl(l):
Reaction at the anode: 2Cl-(l) → Cl2(g) + 2e-
Reaction at the cathode: Na+(l) + e- → Na(l)

For the metals with moderate reactivity (Zn, Fe, Pb, Cu, etc):
The method used is to heat the oxide of the metal with carbon.
For example, heat the mixture of copper(II) oxide with carbon powder.
2CuO(s) + C(s) → 2Cu(s) + CO2(g)

For the metals with low reactivity (Ag, Hg, etc.):
The method used is to heat the oxide of the metal alone.
For example, heat silver oxide alone.
2Ag­­2O(s) → 4Ag(s) + O2(g)

For the metals with very low reactivity (Au, Pt):
It is not necessary to extract the metal because their ores contains the metals but not their compounds.
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