Extraction of Aluminium
Aluminium is extracted from its ore by electrolysis.
For electrolysis to take place the aluminium oxide must be molten because the ions are not free to move in a solid state.
It has a very high melting point and so its first dissolved in cryolite, which lowers its melting point and allows electrolysis to occur at a much lower temperature.
This makes it both cheaper and safer.
Industrial Electrolysis of Brine
Sodium Chloride is a compound of an alkali metal and a halogen.It is found in large quantities in the sea and in underground deposits. Electrolysis of Sodium Chloride solution produces some very important reagents for the chemical industry:
- chlorine gas at the + electrode
- hydrogen gas at - electrode
- sodium hydroxide solution, which is passed out of the cell
The products of Brine have many uses:
- Chlorine used to kill bacteria in water + to manufacture hydrochloric acid, disenfectants, and the plastic PVC
- Hydrogen is used in the manufacture of ammonia and margarine
- Sodium hydroxide is used in the manufacture of soap, paper and ceramics.
Test for chlorine is that it bleaches litmus paper.
Used for electroplating because it protects them from corrosion and improving their appearance.
Also used to purify metals, e.g. the purification of copper. For electrolysis to take place:
- the + electrode needs to be made of impure copper
- the - electrode needs to be made of pure copper
- the solution must contain copper ions
Consequently, the - electrode gets bigger and bigger, while the + electrode slowly dissolves away to nothing. The impurities of copper fall to the bottom of the container as the process takes place.