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Faraday's laws of electrolysis
Intermediate
Mass deposited is proportional to charge.
Mass deposited m = ZIt = (M/nF)It; one faraday (96,485 C) deposits one mole of charge equivalent.
Copper (M = 63.5, n = 2): 1 A for 1 h deposits 1.19 g.
Z is electrochemical equivalent.
In more detail
Faraday's first law says that the mass of a substance deposited during electrolysis is proportional to the charge passed. The second law states that equal charges deposit masses proportional to the substance's equivalent mass.
Real-world uses
- Industrial plating and refining use Faraday's laws to control deposit thickness.
- Coulometry measures charge by measuring the mass deposited.
- Electroplating a spoon with silver depends on the amount of charge passed, which Faraday's laws describe.
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Frequently asked questions
What is the Faraday constant?
About 96,485 coulombs per mole of electrons.
How do I use Faraday's law?
Mass equals charge times molar mass divided by the number of electrons times the Faraday constant.
What does Faraday's first law say?
The mass of substance deposited is proportional to the total charge that passes through the electrolyte.
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