Faraday's laws of electrolysis

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Faraday's laws of electrolysis are a set of scientific laws used in chemistry. They are used to express magnitudes of electrolytic effects. They were first described by Michael Faraday in 1834.

The first law states that the mass of a substance produced by electrolysis is directly proportional to the quantity of the electricity that passes through the cell.

The second law says: since Q, F, and z are constants, the larger the value of M/z (equivalent weight) the larger m will be.

Mathematical form[change | change source]

Faraday's laws can be summarized by


  • m is the mass of the substance liberated at an electrode in gms
  • Q is the total electric charge passed through the substance in coulombs
  • F = 96485.33289(59) C mol−1 is the Faraday constant
  • M is the molar mass of the substance in grams per mol
  • z is the valency number of ions of the substance (electrons transferred per ion).

M/z is the same as the equivalent weight of the substance altered.