Faraday's laws of electrolysis

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Michael Faraday studied the process of electrolysis in detail. He published two laws of electrolysis based on this research which are known as Faraday's laws of electrolysis.

Original form

Faraday's 1st Law of Electrolysis
The mass of a substance produced at an electrode during electrolysis is directly proportional to the number 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.

Modern form

In modern form, Faraday's laws are summarised by:


m is the mass of the substance produced at the electrode
Q is the total electric charge passed through the solution
z is the valence number of ions of the substance (electrons transferred per ion)
F = 96 485 C mol-1 is the Faraday constant
M is the molar mass of the substance

The total charge Q is the integral electric current I(t) over time t:

where T is the total amount of time of the electrolysis.

In the simple case of constant current electrolysis this reduces to:

and leads to

where n is the amount of substance ("number of moles") produced.


  • Serway, Moses, and Moyer, Modern Physics, third edition (2005).

See also


de:Faradaysche Gesetze el:Νόμος ηλεκτρόλυσης eo:Leĝo de Faraday nl:Elektrolysewet van Faraday uk:Закони Фарадея