IUPAC - Faraday’s laws of electrolysis (09075)

Faraday’s laws of electrolysis

https://doi.org/10.1351/goldbook.09075

Faraday’s First Law of electrolysis: Mass

m

of electrochemically-transformed substance is proportional to the charge

Q

passed,

m \propto Q

. Faraday’s Second Law of electrolysis: When the same electric charge (quantity of electricity)

Q

is passed through several electrolytes, the mass

m_{i}

of the substances deposited are proportional to their respective chemical equivalent molar mass,

M_{i} / z_{i}

m_{1} / m_{2} = (M_{1} / z_{1}) / (M_{2} / z_{2})

Notes:

The relationship may be formulated as $m = M Q / z F$ , where $M$ is the molar mass of the substance, $z$ the number of electrons transferred (see: electron number of an electrochemical reaction), and $F$ is the Faraday constant.
Measurement of charge using a coulometer relies on Faraday’s Law.
If reference is made only to ‘Faraday’s Law of electrolysis’ the first law is meant.

Source:
PAC, 2020, 92, 641. (Terminology of Electrochemical Methods of Analysis (IUPAC Recommendations 2019)) on page 653 [Terms] [Paper]

Citation: 'Faraday’s laws of electrolysis' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.09075 RIS BibTex EndNote

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Faraday’s laws of electrolysis