Electrolytic Cells
Chemistry: IB Diploma Higher Level, topic 6.7.4
Electrolytic Cells
Electrochemical cells that undergo reactions that are not thermodynamically favorable are called electrolytic cells. They require an input of voltage for reacions to occur.
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Electrolytic cells
- In galvanic cells, electrical work is done by a redox system on its surroundings.
- Electrons produced by the redox reaction are transferred through an external circuit.
- In electrolytic cells, an external circuit does work on a redox system by imposing a voltage sufficient to drive an otherwise thermodynamically unfavorable reaction.
- This process is known as electrolysis.
Example
- Metallic sodium, Na, and chlorine gas, Cl2, are used in numerous applications.
- Their industrial production relies on the large-scale electrolysis of molten sodium chloride, NaCl(l).
- The reactions associated with this process are:
- Anode: 2Cl−(l)⟶Cl2(g) + 2e−
- Cathode: Na+(l) + e− ⟶ Na(l)
- Cell: 2Na+(l) + 2Cl−(l) ⟶ 2Na(l) + Cl2(g)
Applying voltage
- The cell potential for the above process is negative.
- This indicated that the reaction as written (decomposition of liquid NaCl) is not thermodynamically favorable.
- To force this reaction, a positive potential of magnitude greater than the negative cell potential must be applied to the cell.
Test yourself on Electrolytic Cells
Which of the following is could be the cell potential of an electrolytic cell prior to applying an external voltage?