Electrochemistry
Definition and meaning of Electrochemistry in chemistry.
Electrochemistry is the branch of chemistry that studies the interconversion of electrical energy and chemical energy through oxidation-reduction (redox) reactions. It examines how electron transfer between substances can either generate an electric current or be driven by one.
In more detail
In a galvanic (voltaic) cell, a spontaneous redox reaction is split into separate oxidation and reduction half-reactions at two electrodes connected by an external circuit, producing usable electrical current as electrons flow from anode to cathode. In an electrolytic cell, an external power source forces a nonspontaneous redox reaction to occur, as in electroplating or the electrolysis of water. The cell potential is governed by the Nernst equation, which relates it to the standard electrode potential and reactant/product concentrations, while Faraday's laws quantify the amount of substance produced or consumed per unit of charge passed.
Key facts
| Field | Physical Chemistry |
|---|---|
| Key relation | Nernst equation: E = E° − (RT/nF)lnQ |
| Governing law | Faraday's laws of electrolysis |
| Cell types | Galvanic (spontaneous, produces current) and electrolytic (nonspontaneous, consumes current) |
In the Daniell cell, a zinc electrode is oxidized (Zn → Zn2+ + 2e−) while Cu2+ ions are reduced at a copper electrode (Cu2+ + 2e− → Cu); the spontaneous electron flow through the external wire generates about 1.10 V under standard conditions.
Frequently asked questions
What is the difference between a galvanic cell and an electrolytic cell?
A galvanic cell converts the energy of a spontaneous redox reaction (negative ΔG) into electrical energy, while an electrolytic cell uses an external electrical source to drive a nonspontaneous redox reaction (positive ΔG), such as electroplating or electrolysis.
What is standard electrode potential measured against?
Standard electrode potentials are measured relative to the standard hydrogen electrode (SHE), which is arbitrarily assigned a potential of exactly 0 V under standard conditions.