Faraday
Definition and meaning of Faraday in chemistry.
The faraday, symbol F, is a unit of electric charge equal to the charge carried by one mole of electrons. Its value is approximately 96,485 coulombs per mole. Chemists use it to connect the amount of electric charge passed through a cell to the moles of electrons transferred.
In more detail
The faraday is defined as the product of Avogadro's number and the elementary charge on a single electron. This is written F = NA x e. This links a countable number of particles, one mole of electrons, to a measurable quantity of electric charge.
The constant is central to Faraday's laws of electrolysis, first worked out by Michael Faraday in the 1830s. These laws connect two quantities at an electrode. The mass of a substance produced or consumed is directly proportional to the electric charge passed through the cell.
Using the faraday constant, chemists can calculate exactly how much metal will be deposited or how much gas will be released. They can also find how long an electrolysis process must run to produce a target amount of product. This has enormous industrial value, since processes like aluminum refining and electroplating rely on precise control of these variables.
A common source of confusion is that the faraday, a unit of charge, sounds almost identical to the farad. The farad is the SI unit of electrical capacitance. Despite sharing Michael Faraday's name, the two units measure completely different physical quantities. They should never be substituted for each other in a calculation.
Key facts
| Field | Physical Chemistry |
|---|---|
| Symbol | F |
| Value | About 96,485 C/mol |
| Defined as | F = NA x e (Avogadro constant x elementary charge) |
| Named for | Michael Faraday |
| Key use | Faraday's laws of electrolysis |
Passing one faraday of charge through a solution of silver nitrate deposits exactly one mole of silver metal at the cathode. This follows from the half-reaction Ag+ + e- -> Ag. It requires exactly one mole of electrons for every mole of silver produced.
Frequently asked questions
How is the faraday constant used in electrolysis calculations?
Total charge Q equals moles of electrons times F. Dividing the measured charge by F gives moles of electrons, which stoichiometry then converts to moles of product formed.
Is a faraday the same as a farad?
No. The farad is the SI unit of electrical capacitance, while the faraday is a unit of electric charge. Both are named after Michael Faraday but measure different quantities.
Why is the faraday constant important in industry?
It lets engineers calculate exactly how much metal or gas an electrolysis process will produce from a given amount of electric charge, which is essential for processes like aluminum refining and electroplating.