Electrolysis - concept, application rules and process diagrams
Such a physicochemical process as electrolysis, which takes place with the help of an electrolyzer, is very popular in the metallurgy and chemical industry. To understand the principle of its action, you need to study the definition, nuances and features of the phenomenon.
Electrolysis is a process that occurs when an electric current is applied to an electrolyte and consists in the release of constituent parts by the electrodes.
The significance of the phenomenon lies in the fact that by the action of electricity on ions, it is possible to organize new forms, structures, or even substances themselves. This allows a person to control some of the processes occurring at the molecular level. The laws of this phenomenon in chemistry and physics were discovered by the English scientist Faraday.
The phenomenon occurs with the participation of electrodes, which are divided into cathode and anode:
- cathode - an electrode with a negative charge on which cations are reduced;
- anode - an electrode with a positive charge, where anions are oxidized.
Appliances are most often made from materials that conduct electrical current, such as graphite or most metals. Both devices are connected to the negative and positive poles respectively.
The phenomenon occurs in the following order:
It is very important not to confuse such closely related definitions as hydrolysis and electrolysis. The first phenomenon is the decomposition of a solution of a substance into ions (charged particles) in water.
Faraday's first law
The first law established by Faraday speaks of a direct proportionality between the mass of a substance released during electrolysis and the amount of charge that passed through the electrolyte.
The rule is supported by the formula m = k * q, that is, the product of the charge of a substance by its electrochemical equivalent, which is equal to its mass.
Faraday's second law
This rule, established by Faraday, indicates the relationship between the atomic mass of a substance, the number of possible chemical bonds and the electrochemical equivalent itself.
Thus, the electrochemical equivalent is directly proportional to the atomic mass of the substance, but it is inversely proportional to the valence of the substance.
Electrolysis of molten salts
This type of reaction can be considered using the example of a melt of sodium hydroxide, that is, NaOH.
Sodium hydroxide hydrolysis
Dissociation of hydroxide
NaOH => Na + + OH-
Oxidation and reduction processes
4OH- - 4ē => 2H2O + O2 ↑ (oxidation)
Na + + 1ē => Na0 (recovery)
4NaOH => 4Na + 2H2O + O2 ↑
Electrolysis of salt solutions
The phenomenon can be considered using the example of sodium chloride, which has the formula NaCl.
Sodium chloride electrolysis
Scheme using inert electrodes:
Dissociation of salt
NaCl => Na + + Cl-
Oxidation and reduction processes
2Cl- - 2ē => Cl2 ↑
2H2O + 2ē => H2 ↑ + 2OH-.
2NaCl + 2H2O => H2 ↑ + Cl2 ↑ + 2NaOH.
Thus, the product of the chemical reaction was the production of sodium hydroxide.
It should also be noted such a feature of carboxylic acid salts as their ability to decarboxylate, such as the reaction with potassium acetate:
2CH3COOK + 2H2O => H2 + 2KOH + CH3-CH3 + 2CO2.
The electrolysis of substances is one of the most important topics in the study of chemistry, both inorganic and organic. It is necessary to learn how to solve such problems in order to fully understand the chemical processes and metamorphoses of substances.