Faraday constant
Template:Short description Script error: No such module "Distinguish". Template:Infobox physical quantity In physical chemistry, the Faraday constant (symbol FScript error: No such module "Check for unknown parameters"., sometimes stylized as ℱ) is a physical constant defined as the quotient of the total electric charge (qScript error: No such module "Check for unknown parameters".) by the amount (nScript error: No such module "Check for unknown parameters".) of elementary charge carriers in any given sample of matter: FScript error: No such module "Check for unknown parameters". = q/nScript error: No such module "Check for unknown parameters".; it is expressed in units of coulombs per mole (C/mol). As such, it represents the "molar elementary charge",[1] 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,[1] the Faraday constant has an exactly defined value, the product of the elementary charge (eScript error: No such module "Check for unknown parameters"., in coulombs) and the Avogadro constant (NAScript error: No such module "Check for unknown parameters"., in reciprocal moles):
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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 Template:Physical constants,[1] and there are exactly Template:Physical constants entities per mole,[1] the Faraday constant is given by the product of these two quantities:
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The value of FScript error: No such module "Check for unknown parameters". was first determined in the 1800s by weighing the amount of silver deposited in an electrochemical reaction, in which a measured current was passed for a measured time, and using Faraday's law of electrolysis.[2] 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.[3]
Other common units
- 96.485 kJ per volt–gram-equivalent
- 23.061 kcal per volt–gram-equivalent
- 26.801 A·h/mol
Faraday – a unit of charge
Related to the Faraday constant is the "faraday", a unit of electrical charge. Its use is much less common than of the coulomb, but is sometimes used in electrochemistry.[4] One faraday of charge is the charge of one mole of elementary charges (or of negative one mole of electrons), that is,
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Where N0 is Avogadro's number, the unitless counterpart to NA. Conversely, the Faraday constant F equals 1 faraday per mole. (The farad is an unrelated unit of capacitance, 1 farad = 1 coulomb / 1 volt).
See also
- Farad, the unit of electrical capacitance
- Faraday efficiency
- Faraday's laws of electrolysis
- Faraday cup
References
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- ↑ a b c d Script error: No such module "citation/CS1".
- ↑ NIST Introduction to physical constants
- ↑ Script error: No such module "Citation/CS1".
- ↑ Foundations of Physics, Volume 2, by R. S. Gambhir, 1993, p. 51
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Template:Scientists whose names are used in physical constants Template:Michael Faraday Template:Mole concepts