In physics and chemistry, the Faraday constant,
denoted by the symbol F and named after Michael
Faraday, is the magnitude of electric charge
per mole of electrons. It has the currently
accepted value
9.64853399(24) x 104 C mol-1.
The constant F has a simple relation to two
other physical constants:
where
e ≈ 1.6021766×10−19 C;
NA ≈ 6.022141×1023 mol−1.
NA is the Avogadro constant, and e is the
elementary charge or the magnitude of the
charge of an electron. This relation is true
because the amount of charge of a mole of
electrons is equal to the amount of charge
in one electron multiplied by the number of
electrons in a mole.
One common use of the faraday constant is
electrolysis. One can divide the amount of
charge in coulombs by the Faraday constant
in order to find the amount of the element
that has been oxidized.
The value of F was first determined 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. Research is continuing into
more accurate ways of determining the interrelated
constants F, NA, and e.
Other Common Units of Faraday's Constant
96,485 J per volt gram equivalent
23.061 kcal per volt gram equivalent
26.801 A·h/mol
Faraday unit of charge
Related to Faraday's constant is the "faraday",
a unit of electrical charge. It is much less
common than the coulomb, but sometimes used
in electrochemistry. One faraday of charge
is the magnitude of the charge of one mole
of electrons, i.e. 96485.3365(21) C.
Expressed in faradays, the Faraday constant
F equals "1 faraday of charge per mole".
This faraday unit 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 how much he
wants for his entire comic book inventory.
He says "the speed of light expressed as dollars"
and Mr. Burns says to Smithers, "give him
Faraday's Constant." The check is written
for $96,485.34.
See also
Faraday cage
Faraday efficiency
Faraday's law of electrolysis
Faraday's law of Electromagnetic induction
References
