This I/GCSE Chemistry blog post will continue on with part two of learning electrolysis, let's get started!
In the cell
In order to carry out electrolysis the compound must either be molten or in solution so that the ions can move to the relevant electrodes.
Molten compound
- If the compound is molten it is easy to determine what will be formed at each electrode.
- Non metals go to the anode. Metals go to the cathode.
Solution
- If the compound is solution then the water also forms ions. If the metal is less reactive than hydrogen then metal forms at the cathode.
- If it is more reactive than the hydrogen forms at the cathode and the metal stays in solution.
Aluminium extraction
- Aluminium is extracted from an ore called Bauxite which contains aluminim oxide.
- Bauxite is mixed with cryolite to reduce the temperature required to keep the ore molten.
- However very high temperatures are still required so furnaces are used to heat the mixture.
- The aluminium ions are reduced and gain 3 electrons whilst the oxygen is oxidiesed and loses 2 electrons.
Electrolysis of brine
Brine is a solution of sodium chloride in water.
Brine contains sodium, chlorine, hydrogen and hydroxide ions.
When electrolysed it forms hydrogen at the cathode, chlorine at the anode and sodium hydroxide in solution.
Uses for products
- Chlorine
is used to kill bacteria (drinking water, swimming pools) and to make bleach, disinfectant and plastic.
- Hydrogen
is used to make margarine and hydrochloric acid.
- Sodium hydroxide
is a strong alkali and has many uses in soap, papermaking , neutrilising acis ad controlling pH.
That's the end of part 2! Well done!
References:
https://www.google.com/url?sa=i&url=https%3A%2F%2Fchem.libretexts.org%2FBookshelves%2FAnalytical_Chemistry%2FSupplemental_Modules_(Analytical_Chemistry)%2FElectrochemistry%2FElectrolytic_Cells&psig=AOvVaw2Bm6N3jC0kBHYurTGMUf1s&ust=1628510489821000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCNDnpL-0ofICFQAAAAAdAAAAABAD