Faraday: definition in chemistry
Faraday: The electric charge carried by one mole of electrons, about 96,485 coulombs. This value is called the Faraday constant (F).
The Faraday constant links the electric charge passed through a cell to the amount of substance that reacts at an electrode. It equals Avogadro's number multiplied by the charge of one electron, and it is named after Michael Faraday, who worked out the laws of electrolysis in the 1830s. Chemists use it to calculate how much metal a current will deposit and to relate a cell's voltage to the energy of its reaction.
Examples
- Depositing 1 mole of silver from Ag⁺ ions takes about 96,485 C
- Depositing 1 mole of copper from Cu²⁺ ions takes twice as much charge
- Making 1 mole of aluminum from Al³⁺ ions takes about 289,000 C
- A current of 1 ampere must flow for about 26.8 hours to deliver 96,485 C
On the periodic table
An ion's charge, which for many metals follows from the group, sets how much charge each mole needs: Na⁺ needs one mole of electrons, Mg²⁺ two and Al³⁺ three.