In electrochemical reactions, electrons are transferred from one chemical to another. How many grams or moles of the chemicals will react depends on how many electrons or moles of electrons are transferred. This in turn depends on how much electric current is used and how long it runs.
There is a special name for one mole of electrons. One mole of electrons is called a Faraday. Actually, a Faraday is the amount of electric charge on one mole of electrons, rather than being the electrons themselves.
The amount of a chemical that reacts can be related to the current in amps (which can be expressed as coulombs per second) and the time that the current flows (measured in seconds) by this equation. Some conversion factors are necessary to change from the physical measurements of time and current to the chemical measurements of moles. The last factor shown here deals with the fact that different chemicals require a different number of electrons to change from one oxidation state to another. For example, sodium requires one electron to change from Na+ to Na, but aluminum requires three electrons to change from Al3+ to Al.
In this course, what you need to know about Faraday calculations is this descriptive relationship between Faradays, electrons, current, time and extent of reaction. You won't be called upon to carry out these calculations.
E-mail instructor: Eden Francis
Clackamas Community College