Faraday's Law of Electrolysis
Definition and meaning of Faraday's Law of Electrolysis in chemistry.
Faraday's law of electrolysis quantifies the relationship between electric charge and the amount of substance produced or consumed at an electrode during electrochemical reactions. The mass of a substance deposited is directly proportional to the total quantity of electric charge that flows through the electrolytic cell.
In more detail
Mathematically, the law is expressed as m = (M × Q) / (n × F), where m is the mass of substance, M is the molar mass, Q is the electrical charge in coulombs, n is the number of electrons transferred per formula unit, and F is Faraday's constant (96,485 C/mol). This fundamental relationship demonstrates that identical quantities of electric charge produce chemically equivalent amounts of different substances, scaled by their atomic and molecular masses. The law is essential for predicting product yield in industrial processes like electroplating, metal refining, and chemical synthesis.
Key facts
| Field | Physical Chemistry |
|---|---|
| Faraday Constant | 96,485 C/mol (coulombs per mole of electrons) |
| Discovered | Michael Faraday, 1834 |
| Formula | m = (M × Q) / (n × F) |
During copper electroplating, the cathode reaction is Cu2+ + 2e- → Cu, so n = 2 electrons are required per copper ion deposited. Passing 96,485 coulombs of charge through the electrolytic cell delivers exactly 1 mole of electrons, which deposits only 0.5 mole of copper metal, 31.75 grams (using a molar mass of 63.5 g/mol), at the cathode. If only 48,243 coulombs pass (about half the charge), only 0.25 mole, or 15.875 grams, of copper deposits.
Frequently asked questions
Why is Faraday's law important in industry?
It enables precise control and prediction of product mass in electroplating, metal refining, and electrochemical synthesis by relating measurable electrical parameters (current and time) directly to the amount of chemical change.
What does n represent in the formula?
The variable n is the number of electrons transferred per ion in the redox reaction, such as 2 for Cu2+ (Cu2+ + 2e- → Cu), 1 for Ag+ (Ag+ + e- → Ag), or 3 for Al3+ (Al3+ + 3e- → Al).