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physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistica ...
, the Faraday constant, denoted by the symbol and sometimes stylized as ℱ, is the
electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
per
mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America * Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
of elementary charges. It is named after the English
scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
Michael Faraday Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...
. Since the 2019 redefinition of SI base units, which took effect on 20 May 2019, the Faraday constant has the exactly defined value given by the product of the elementary charge ''e'' and
Avogadro constant The Avogadro constant, commonly denoted or , is the proportionality factor that relates the number of constituent particles (usually molecules, atoms or ions) in a sample with the amount of substance in that sample. It is an SI defining c ...
''N''A: : : :.


Derivation

The Faraday constant can be thought of as the conversion factor between the mole (used in chemistry) and the coulomb (used in physics and in practical electrical measurements), and is therefore of particular use in
electrochemistry Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...
. Because 1 mole contains exactly entities, and 1 coulomb contains exactly elementary charges, the Faraday constant is given by the quotient of these two quantities: :. One common use of the Faraday constant is in electrolysis calculations. One can divide the amount of charge (the current integrated over time) by the Faraday constant in order to find the chemical amount of a substance (in moles) that has been electrolyzed. The value of was first determined by weighing the amount of
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
deposited in an electrochemical reaction in which a measured
current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...
was passed for a measured time, and using
Faraday's law of electrolysis Faraday's laws of electrolysis are quantitative relationships based on the electrochemical research published by Michael Faraday in 1833. First law Michael Faraday reported that the mass (m) of elements deposited at an electrode is directly prop ...
.


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 Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
. It is much less common than the coulomb, but is sometimes used in electrochemistry.''Foundations of Physics, Volume 2'', by R. S. Gambhir, 1993, p. 51
/ref> One faraday of charge is the magnitude of the charge of one mole of electrons, i.e., :1 faraday = ''F'' × 1 mol = Conversely, the Faraday constant ''F'' equals 1 faraday per mole. The faraday is not to be confused with the farad, an unrelated unit of
capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized ar ...
().


Popular media

''
The Simpsons ''The Simpsons'' is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical depiction of American life, epitomized by the Simpson family, which consists of Homer, Marge, Bart, Lisa, ...
'' episode " Dark Knight Court" has
Mr. Burns Charles Montgomery Plantagenet Schicklgruber "Monty" Burns, usually referred to as Mr. Burns, Monty, or C. Montgomery Burns, is a recurring character and the main antagonist of the animated television series ''The Simpsons'', voiced initially by ...
asking
Comic Book Guy Jeff Albertson, commonly known as Comic Book Guy, is a recurring fictional character in the animated television series ''The Simpsons''. He is voiced by Hank Azaria and first appeared in the second-season episode " Three Men and a Comic Book", wh ...
how much he wants for his entire
comic book A comic book, also called comicbook, comic magazine or (in the United Kingdom and Ireland) simply comic, is a publication that consists of comics art in the form of sequential juxtaposed panels that represent individual scenes. Panels are of ...
inventory. He says "the
speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...
expressed as
dollars Dollar is the name of more than 20 currencies. They include the Australian dollar, Brunei dollar, Canadian dollar, Hong Kong dollar, Jamaican dollar, Liberian dollar, Namibian dollar, New Taiwan dollar, New Zealand dollar, Singapore dollar, U ...
" and Mr. Burns tells Smithers to "just give him Faraday's Constant". The check is written for $96,485.34.


See also

* Faraday cage *
Faraday efficiency Faraday efficiency (also called ''faradaic efficiency'', ''faradaic yield'', ''coulombic efficiency'' or ''current efficiency'') describes the efficiency with which charge (electrons) is transferred in a system facilitating an electrochemical reacti ...
*
Faraday's laws of electrolysis Faraday's laws of electrolysis are quantitative relationships based on the electrochemical research published by Michael Faraday in 1833. First law Michael Faraday reported that the mass (m) of elements deposited at an electrode is directly pro ...
* Faraday's law of induction *
Faraday cup A Faraday cup is a metal (conductive) cup designed to catch charged particles in vacuum. The resulting current can be measured and used to determine the number of ions or electrons hitting the cup. The Faraday cup was named after Michael Fara ...


References

{{Michael Faraday Electrochemical concepts Physical constants Michael Faraday Units of electrical charge Units of amount of substance