What is an Electrochemical Cell?
An electrochemical cell is a device that converts chemical energy into electrical energy, or uses electrical energy to drive a chemical reaction. There are two types: galvanic cells (spontaneous) and electrolytic cells (non-spontaneous).
An electrochemical cell couples a redox reaction to electron flow through an external circuit. Galvanic cells produce electricity; electrolytic cells consume it.
- •Spontaneous redox reaction
- •Anode (−) oxidized
- •Cathode (+) reduced
- •Produces electric current
- •Electrons flow: − to +
- •Non-spontaneous reaction
- •Anode (+) oxidized
- •Cathode (−) reduced
- •Consumes electric current
- •Electrons forced: − to +
Step-by-step worked examples
In a Zn–Cu galvanic cell, which electrode is the cathode and what happens there?
Cu is less reactive than Zn. Zn is oxidized (anode). Cu²⁺ is reduced at Cu (cathode) → Cu²⁺ + 2e⁻ → Cu
In electrolysis of water using inert electrodes, name the product at the anode.
Non-spontaneous reaction, powered by DC source. Anode is positive. At anode (oxidation): 2H₂O → O₂ + 4H⁺ + 4e⁻ Product = O₂ gas
How do anodes differ between galvanic and electrolytic cells?
Galvanic: anode is negative (−) terminal, where oxidation happens spontaneously. Electrolytic: anode is positive (+) terminal, oxidation is forced by external voltage.
Flashcards
Quick quiz
Q1.In a galvanic cell, the anode is the ___ terminal.
Q2.Electrolytic cells differ in that they are…
Q3.Which equation represents reduction at the cathode?
Q4.The salt bridge in a galvanic cell…
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Common mistakes
Galvanic cells have positive anode. — Correct: Galvanic cells have negative anode; positive cathode. (Electrolytic is reversed.)
Electrons flow from cathode to anode inside the cell. — Correct: Ions flow inside; electrons flow through the external circuit (anode → cathode).
Both electrodes are always made of the same material. — Correct: Electrodes are often different metals (Zn and Cu, for example).
Electrolytic cells produce electricity like galvanic cells. — Correct: Electrolytic cells consume electricity; galvanic cells produce it.
FAQ
What is an electrochemical cell definition?
An electrochemical cell converts redox reactions into electrical energy (galvanic) or uses electricity to drive reactions (electrolytic).
What are examples of electrochemical cells?
Galvanic: battery, Zn–Cu cell. Electrolytic: water electrolysis, metal plating, chlor–alkali process.
Why is the salt bridge important in galvanic cells?
It allows ions to diffuse between compartments, preventing charge imbalance and maintaining continuous current.
How do I identify anode and cathode?
Anode = oxidation (loses e⁻). Cathode = reduction (gains e⁻). In galvanic: anode is −, cathode is +.