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, statistical ...

, 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 respecti ...

per mole of

elementary charge The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a funda ...

s. 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 philosophica ...

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 inductio ...

. 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

''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 The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). In the present version of the SI it is equal to the electric charge delivered by a 1 ampere constant current in 1 second and to elementary ch ...

(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 outc ...

. 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 was passed for a measured time, and using Faraday's law of electrolysis.

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. It is much less common than the

, 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 The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base unit ...

, 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 a ...

().

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 Simpson, Homer, Marge ...

'' episode " Dark Knight Court" has Mr. Burns asking Comic Book Guy 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 panel (comics), panels that represent individual scenes. ...

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 fo ...

expressed as dollars" and Mr. Burns tells Smithers to "just give him Faraday's Constant". The check is written for $96,485.34.

References

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

Derivation

Other common units

Faraday – a unit of charge

Popular media

See also

References