constant

faraday constant

Charge of one mole of electrons.
Value
\(F = 96485.33212\)coulomb per mole
17 related articles

Description

The Faraday constant, F, is the magnitude of electric charge carried by one mole of electrons, approximately 96,485.33212 C/mol. It bridges the macroscopic world of electrolysis and electrochemistry with the microscopic world of individual charges: one mole of electrons carries exactly F coulombs. It is named after Michael Faraday, whose laws of electrolysis established the quantitative link between charge and chemical change.

History

Faraday formulated his laws of electrolysis in 1834, but the constant itself was first determined numerically by later researchers, notably by John Strutt (Lord Rayleigh) and others in the late 19th century. The modern precise value comes from measurements of the elementary charge and Avogadro's number.

How it works

The constant is defined as F = N_A × e, where N_A is Avogadro's number and e is the elementary charge. In electrolysis, passing a current I for time t deposits a mass m of a substance with molar mass M and valence z, following m = (M × I × t) / (z × F). This relation allows chemists to calculate how much material is produced or consumed in electrochemical cells, from batteries to electroplating.

In practice

The Faraday constant is used in electroplating, battery design, fuel cells, and in analytical chemistry for coulometric titration—a technique that measures the amount of substance by the charge passed.

Fun fact

The Faraday constant is so large that one mole of electrons—about 6 × 10²³ particles—would take over 11 days to flow through a standard 100-watt light bulb.

Concept graph →

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