In physical chemistry, the Faraday constant (symbol , sometimes stylized as ℱ) is a physical constant defined as the quotient of the total electric charge () by the amount () of elementary charge carriers in any given sample of matter: it is expressed in units of coulombs per mole (C/mol).
As such, it represents the "molar elementary charge", that is, the electric charge of one mole of elementary carriers (e.g., protons). It is named after the English scientist Michael Faraday. Since the 2019 revision of the SI, the Faraday constant has an exactly defined value, the product of the elementary charge (, in coulombs) and the Avogadro constant (, in reciprocal moles):
:
Derivation
The Faraday constant can be thought of as the proportionality factor between the charge in coulombs (used in physics and in practical electrical measurements) and the amount of substance in moles (used in chemistry), and is therefore of particular use in electrochemistry, particularly in electrolysis calculations. Because the elementary charge is exactly , and there are exactly entities per mole, Until about 1970, the most reliable value of the Faraday constant was determined by a related method of electro-dissolving silver metal in perchloric acid.
Faraday – a unit of charge
Related to the Faraday constant is the "faraday", a unit of electrical charge. One faraday is the amount of charge in one mole of electrons:
Where N<sub>0</sub> is Avogadro's number. A faraday will electrodeposit one mole of silver metal atoms.
See also
- Farad, the unit of electrical capacitance
- Faraday efficiency
- Faraday's laws of electrolysis
- Faraday cup