Electrolysis
The word electrolysis is derived from the two words electro (means electricity) and lysis (meaning breakdown). So, the word electrolysis means the breaking down of compounds, to their basic elements, using electricity.
Important terms which are used frequently in electrolysis:
1) Electrolyte: liquid which conducts electricity.
2) Conductor: a solid which conducts electricity. For example copper, iron, aluminium.
3) Semi-conductor: a solid which partially conducts electricity. For example silicon, germanium.
4) Insulator: a solid which doesn't conduct electricity at all. For example polythene, wood.
5) Strong electrolyte: a liquid that conducts electricity. For example strong acid or alkali (H2SO4, HCl, NaOH solution), solutions of ionic compounds (salts) etc.
6) Weak electrolyte: a liquid which conducts electricity partially. E.g. weak acids or alkali, water etc.
7 Non electrolyte: a liquid which does not conduct electricity. For example organic liquids (such as ethanol, methylbenzene).
8) Anode: positive electrode of the electrolysis cell.
9) Cathode: negative electrode of the electrolysis cell.
10) Anion: negative ion formed by gain of the electrons by non-metals.
11) Cation: positive ion formed by the loss of electrons usually by metals.
12) Coloumb : is the electrical charge unit.
13) Faraday: 1 faraday is amount of charge carried by 1 mole of electrons.
Electrolytes conduct electricity because they have free ions. The diagram drawn above illustrates the statement. When the electrodes are dipped in an electrolyte and voltage is applied, the free ions are attracted to the oppositely charged electrodes. At the cathode cations lose their additional electron and then are discharged. The electrons, lost by the anions, travel to the cathode and are gained by the cations, which are also discharged. Thus, electrically neutral particles are formed at both electrodes.
Non-electrolytes have no ions and so are incapable of conducting electricity.
Ionic compounds do not conduct electricity in solid state because the ions are held together in strong electrostatic force of attraction and are not free to move. They conduct electricity only when molten or in solution as then the ions are free to move.
Electrolysis of different compounds can be understood as follows:
When liquids containing only two ions are electrolysed (for example, molten NaCl, molten PbBr2 etc.) the result of electrolysis is straightforward and can be easily predicted.