Faraday's law of electrolysis
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Faraday's law of electrolysis predicts the mass of material that will be deposited at an electrode during electrolysis. It was originally stated as two separate laws by Michael Faraday in 1834.
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[edit] Original form
- Faraday's 1st Law of Electrolysis
- The mass of a substance produced at an electrode during electrolysis is proportional to the number of moles of electrons (the quantity of electricity) transferred at that electrode.
- Faraday's 2nd Law of Electrolysis
- The number of Faradays of electric charge required to discharge one mole of substance at an electrode is equal to the number of "excess" elementary charges on that ion.
[edit] Modern form
In modern form, Faraday's law states:
where
- m is the mass of the substance produced at the electrode (in grams),
- Q is the total electric charge that passed through the solution (in coulombs),
- q is the electron charge = 1.602 x 10-19 coulombs per electron,
- n is the valence number of the substance as an ion in solution (electrons per ion),
is Faraday's constant,- M is the molar mass of the substance (in grams per mole), and
- NA is Avogadro's number = 6.022 x 1023 ions per mole.
In practice, the total charge Q is calculated by integrating the electric current I(t) over time t:
where T is the total amount of time of the electrolysis.
[edit] References
- Serway, Moses, and Moyer, Modern Physics, third edition (2005).
[edit] See also
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