Electrolytic Cells
An Electrolytic Cell is an electrochemical cell that uses electrical energy to drive a non-spontaneous chemical reaction. Unlike galvanic cells (which produce electricity spontaneously), electrolytic cells consume electrical energy to cause chemical changes. They are widely used in industrial processes like electroplating, electrorefining, and the decomposition of compounds.
Table of contents
- What is an electrolytic cell?
- Basic components
- Working principle
- Examples
- Electrolytic vs Galvanic
- Quiz
- MCQs
- FAQ
- References & links
Introduction
An electrolytic cell is an electrochemical cell where electrical energy is consumed to force a non-spontaneous chemical reaction. Unlike galvanic cells, electrolytic cells require an external power source (battery or DC supply) to operate and are widely used in industry for deposition, purification, and decomposition processes.
Basic Components of an Electrolytic Cell
- Electrolyte: Molten salt or aqueous ionic solution that conducts ions.
- Electrodes: Two conductors (anode and cathode) immersed in the electrolyte where oxidation and reduction occur.
- Power supply: External DC source that drives the reaction by applying sufficient voltage.
Working Principle
On applying an external voltage, ions migrate: cations move to the cathode (gain electrons → reduction) and anions move to the anode (lose electrons → oxidation). The power supply forces the non-spontaneous redox reaction to proceed, giving chemical products such as deposited metals, gases or purified elements.
Cations → cathode (reduction); Anions → anode (oxidation).
Examples of Electrolytic Cells
- Electrolysis of molten NaCl: Produces Na (cathode) and Cl₂ (anode).
- Electroplating: Deposition of a thin metal layer (e.g., Ni or Ag) on an object for protection/appearance.
- Electrorefining: Purification of metals such as copper — impure metal used as anode, pure metal collects at cathode.
Electrolytic Cell vs Galvanic Cell
| Aspect | Electrolytic Cell | Galvanic Cell |
|---|---|---|
| Energy conversion | Electrical energy → Chemical energy | Chemical energy → Electrical energy |
| Spontaneity | Non-spontaneous | Spontaneous |
| Electrode polarity | Anode is positive; Cathode is negative | Anode is negative; Cathode is positive |
| Examples | Electroplating, electrolysis of water, molten salt electrolysis | Dry cell, Daniell cell, fuel cells |
Quiz: Test Your Knowledge
Q1: What is an electrolytic cell?
Answer: An electrolytic cell uses electrical energy to drive a non-spontaneous chemical reaction.
Explanation: The external power source forces the required redox reaction that would not occur spontaneously.Q2: Which electrode is positive in an electrolytic cell?
Answer: The anode is positive and the cathode is negative.
Explanation: The external source pulls electrons from the anode (making it positive) and pushes them to the cathode.Q3: Name two industrial applications of electrolytic cells.
Answer: Electroplating and electrorefining.
Explanation: Electroplating deposits protective or decorative metal; electrorefining yields high purity metals.Q4: What happens to cations and anions during electrolysis?
Answer: Cations move to the cathode and are reduced; anions move to the anode and are oxidized.
Explanation: This migration maintains charge balance while allowing redox reactions at electrodes.
Multiple Choice Questions
- In an electrolytic cell, the reaction is:
a) Spontaneous
b) Non-spontaneous
c) Equilibrium
d) Irreversible
Explanation: External energy is required to drive the reaction. - The electrode connected to the positive terminal of the battery is:
a) Anode
b) Cathode
c) Salt bridge
d) Electrolyte
Explanation: The positive terminal draws electrons away from the anode making it positive. - Which of the following is an application of electrolytic cells?
a) Dry cell
b) Daniell cell
c) Electroplating
d) Voltaic pile
Explanation: Electroplating deposits a metal layer using an electrolytic setup. - In electrolysis, cations move toward:
a) Anode
b) Cathode
c) Salt bridge
d) None of these
Explanation: Cations are positively charged and are attracted to the negatively charged cathode. - Electrolytic cells convert:
a) Chemical energy to electrical energy
b) Electrical energy to chemical energy
c) Heat energy to chemical energy
d) Mechanical energy to electrical energy
Explanation: They use electrical power to cause chemical transformations.
MCQ Answers
- b) Non-spontaneous
- a) Anode
- c) Electroplating
- b) Cathode
- b) Electrical energy to chemical energy
Frequently Asked Questions
Q: Can electrolysis produce pure elements?
A: Yes — electrolysis (e.g., electrorefining, molten salt electrolysis) can produce or purify metals like copper, sodium, and aluminium when conditions are optimized.
Q: Is electroplating the same as electrolysis?
A: Electroplating is a type of electrolysis where the desired outcome is to deposit a thin metal layer onto a substrate; both are electrolytic processes but with different goals.
Q: Where can I learn more about practical electrolytic setups?
A: Practical guides and laboratory manuals on electrochemistry, manufacturer datasheets for power supplies and plating baths, and CHEMASH internal resources on electrochemistry (internal link:
- Electrolysis overview — Wikipedia: Electrolysis
