What industry uses it for
Electrolysis is widely used in many kinds of industrial production. Some of them are listed below.
Extracting metals from their ores
Sodium metal by electrolysing molten sodium chloride; aluminium metal from bauxite.
Purifying metals
The copper first obtained from copper-bearing minerals is impure; it is purified by electrolysis.
Electroplating
Coating an object with a metal: gold on silver jewellery; nickel or chromium on steel.
Making sodium hydroxide
Industrial production of sodium hydroxide (the diaphragm cell method).
Why industry pays for electricity
Metals such as sodium and aluminium are high in the activity series. Their compounds are very stable: heating with carbon, which extracts iron, cannot pull the oxygen or chlorine away from them. Electrolysis can, because it forces electrons onto the metal ions directly — the same forced, non-spontaneous reaction you saw in the electrolytic cell. The cost is a great deal of electricity, which is why aluminium smelters are often built next to hydroelectric power stations. The other three uses rely on the ideas of the last pages: copper refining and electroplating use a metal anode that dissolves (rule 7), and sodium hydroxide is what is left when brine is electrolysed.
Links back
Grade 10 showed how the activity series decides the way a metal is extracted: the most reactive metals by electrolysis, the middle ones by heating with carbon. This page is where that top row gets its explanation.
Four big uses
Extracting reactive metals, purifying copper, electroplating, and making sodium hydroxide.