Electrolytic Cells
Definition and meaning of Electrolytic Cells in chemistry.
Electrolytic cells are electrochemical devices that use an external source of electrical energy to drive a non-spontaneous redox reaction, converting electrical energy into chemical energy.
In more detail
An external power source forces electrons through the circuit, pushing oxidation at the anode and reduction at the cathode in the direction opposite to what would occur spontaneously. Because the reaction is non-spontaneous, the applied voltage must exceed the cell's own reverse potential to proceed. Electrolytic cells are the basis of electrolysis, electroplating, electrorefining of metals, and industrial processes like the chlor-alkali process and aluminum production (Hall-Héroult process).
Key facts
| Field | Physical Chemistry |
|---|---|
| Energy conversion | Electrical energy to chemical energy |
| Anode | Oxidation; connected to positive terminal |
| Cathode | Reduction; connected to negative terminal |
In the electrolysis of molten sodium chloride, an external voltage source reduces Na+ ions to liquid sodium metal at the cathode while oxidizing Cl- ions to chlorine gas at the anode.
Frequently asked questions
How does an electrolytic cell differ from a galvanic cell?
A galvanic (voltaic) cell generates electrical energy from a spontaneous redox reaction, whereas an electrolytic cell consumes electrical energy from an external source to force a non-spontaneous redox reaction to occur.
Which electrode is negative in an electrolytic cell?
The cathode is negative in an electrolytic cell because it is wired to the negative terminal of the external power supply; this is opposite to a galvanic cell, where the cathode is positive.