Faraday’s electrolysis laws

Farady’s laws of electrolysis : express quantitative relationships based on electrochemical research published by Michael Faraday in 1834 .


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  • 1 Introduction
  • 2 Faraday’s first law (first law of electrolysis)
  • 3 Second Faraday’s law (second law of electrolysis)
  • 4 Faraday’s Unified Law (Unified Electrolysis Law)
  • 5 Sources


Liquids are conductors of electric current (electrolytes, second-class conductors) if, under the action of an external electric field, the ordered movement of ions can take place in them.
The orderly movement of ions in conductive liquids occurs in the electric field created by the electrodes, that is, conductors attached to the poles of an electrical energy source . The positive electrode is called the anode and the negative electrode is called the cathode . Positive ions (cations) move towards the cathode and negative ions (anions) move towards the anode. The electric current in the electrolytes is accompanied by the phenomenon of electrolysis , detachment in the electrodes of the component parts of the dissolved substances or others, resulting from secondary reactions in the electrodes.

Faraday’s first law (first law of electrolysis)

The mass M of substance that emerges from the electrode is directly proportional to the electric charge Q that passes through the electrolyte if a continuous current of intensity I is passed through it during time t .

The proportionality coefficient k is called the electrochemical equivalent of the substance. This coefficient is numerically equal to the mass of substance released when the unit of electric charge passes through the electrolyte and depends on the chemical nature of the substance .

Second Faraday’s law (second law of electrolysis)

The electrochemical equivalents of the elements are directly proportional to their chemical equivalents

Where C is some universal constant for all elements and kx is the chemical equivalent

Here A is the atomic mass of the element (in kg / mol), and z is its valence. So that


The Faraday constant, also known as the Faraday number.

Faraday’s Unified Law (Unified Electrolysis Law)

m = M (X / z *) It / F  (96 500 C = 1 Faraday (F)) It
allows us to clarify the physical meaning of F, because precisely when M = A / z, the number of Faraday F = Q. The quantity of substance equal to 1 / z moles is called the gram-equivalent. When z = 1, the gram equivalent of the substance is equal to one mole. The Faraday constant is numerically equal to the electric charge that must be passed through the electrolyte for a gram equivalent of substance to be released from the electrode.


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