Faraday's law of electrolysis, formulated by the English scientist Michael Faraday, describes the quantitative relationship between the amount of substance produced or consumed during an electrolysis process and the amount of electric charge passed through an electrolytic cell. It provides fundamental principles for understanding and calculating electrochemical reactions.
Faraday's first law of electrolysis states that "the mass of any substance deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of electricity passed through the electrolyte."
Mathematically, this can be expressed as:
m = ZIt
Where:
- m is the mass of the substance deposited or liberated at the electrode (in grams),
- Z is the electrochemical equivalent of the substance (in grams per coulomb or amperes per gram),
- I is the electric current flowing through the cell (in amperes), and
- t is the time of electrolysis (in seconds).
The electrochemical equivalent (Z) is a constant specific to the substance being electrolyzed and is experimentally determined. It represents the amount of substance deposited or liberated per unit charge.
Faraday's second law of electrolysis states that "the masses of different substances deposited or liberated by the same quantity of electricity are directly proportional to their chemical equivalent weights."
The chemical equivalent weight (E) is the ratio of the molar mass of the substance to the number of electrons exchanged during the electrolytic process.
Mathematically, this can be expressed as:
m1/m2 = E1/E2
Where:
- m1 and m2 are the masses of different substances deposited or liberated,
- E1 and E2 are the chemical equivalent weights of the respective substances.
These laws imply that the amount of substance produced or consumed during electrolysis is directly related to the electric charge passing through the cell and the stoichiometry of the chemical reaction. They provide a quantitative understanding of the relationship between electricity and chemical transformations in electrolytic cells.
Faraday's laws have several practical applications, such as determining the chemical composition of compounds, calculating electrode efficiencies, and predicting the amount of substance produced in industrial electrolytic processes. They form the basis for the quantitative study of electrochemistry and are essential in various fields, including electroplating, battery technology, and industrial chemical synthesis.