Faraday constant

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In chemistry and physics, the Faraday constant F is the amount of charge (in absolute value) in one mole of electrons or one mole of monovalent (singly charged) ions. Its value[1] is

where NA is Avogadro's constant and e is the charge of an electron.

The constant F must be carefully distinguished from the unit F (the faraday) which is a unit of capacitance.

The constant and the unit are named after the British physicist Michael Faraday.

Before electrons were discovered and a value for Avogadro's number was known, Faraday discovered (1833) that in electrolysis the amount of charge F necessary to deposit one mole of monovalent ions on an electrode (cations on the cathode, anions on the anode) is always the same, irrespective of the kind of ions. For a long time weighing the amount of silver—which in solution is the cation Ag+—deposited during electrolysis was the accepted manner of measuring electric charge and electric current.


  1. Obtained from NIST on December 16, 2007