In
physical chemistry, the Faraday constant, denoted by the symbol and sometimes stylized as ℱ, is the
electric charge 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 research to advance knowledge in an area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosoph ...
Michael Faraday. Since the
2019 redefinition of SI base units
In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants, rather than human artifacts such as the standard kilogram.
Effective 20 May 2019, the 144 ...
,
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 ''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. 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 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 ().
Popular media
'' The Simpsons'' episode " Dark Knight Court" has Mr. Burns 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 inventory. He says "the speed of light 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's laws of electrolysis
* Faraday's law of induction
* Faraday cup
References
{{Michael Faraday
Electrochemical concepts
Physical constants
Michael Faraday
Units of electrical charge
Units of amount of substance