Faraday constant: Difference between revisions
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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 singly charged ions. Its value<ref>Obtained from [http://physics.nist.gov/cgi-bin/cuu/Value?f NIST] on December 16, 2007</ref> is | 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<ref>Obtained from [http://physics.nist.gov/cgi-bin/cuu/Value?f NIST] on December 16, 2007</ref> is | ||
:<math> | :<math> | ||
F = e N_\mathrm{A} = 96\,485.339\,9\,\, \mathrm{C/mol}, | F = e N_\mathrm{A} = 96\,485.339\,9\,\, \mathrm{C/mol}, | ||
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The constant and the unit are named after the British physicist [[Michael Faraday]]. | 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 | 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 ([[cation]]s on the cathode, [[anion]]s 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<sup>+</sup>—deposited during electrolysis was the accepted manner of measuring electric charge and electric current. | ||
==Reference== | ==Reference== | ||
Revision as of 09:56, 16 December 2007
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.