By the end of this section, learners will be able to:

• describe electrolytic cells and their relationship to galvanic cells.
• perform various calculations related to electrolysis.

In galvanic cells, chemical energy is converted into electrical energy. The opposite is true for electrolytic cells.

In electrolytic cells, electrical energy causes non-spontaneous reactions to occur in a process known as electrolysis.

Electrolysis is a process in which electrical energy is used to produce chemical changes. This process is carried out in an electrochemical cell known as an electrolytic or electrolysis cell. A typical electrolysis cell contains a source of direct electric current, an electrolyte and connecting wires that join the source to the electrodes.

Electrodes are strips of metal or graphite that allow electrons to leave or enter the electrolytes. They can be chemically active or inert. Active electrodes directly take part in reactions. Examples include zinc and magnesium. Inert electrodes do not directly take part in chemical reactions. They only serve to transfer electrons. Examples include platinum and graphite.

Thus, the cathode is the electrode at which reduction occurs and the anode is the electrode at which oxidation takes place.

Difference between Galvanic cell and electrolytic cell

1. Definition of Galvanic cell and electrolytic cell: In galvanic cells there are spontaneous redox processes that allow continuous flow of electrons through the conductor, whereby the chemical energy is converted into electrical energy.

2. Technique of Galvanic cell and electrolytic cell: Galvanic cells generate electricity with the aid of chemical reactions. In electrolytic cells, an electric current is used for development of a chemical reaction, utilizing an external source along the way.

3. Design of Galvanic cell and electrolytic cell: Galvanic cells consists of two different electrodes immersed in solutions of their ions that are separated by a salt bridge. Electrolytic cells consist of an electrolytic container in which two electrodes are connected to a d.c. source.

4. Electrode polarity in Galvanic cell and electrolytic cell: In galvanic cells, the anode is the negative and the cathode is the positive electrode. In electrolytic cells, the opposite occurs.

5. Application of Galvanic cell and electrolytic cell: Galvanic cells are used as a source of electrical current, and are more commonly referred to as batteries or accumulators. Electrolytic cells have different practical uses, some of them being making hydrogen and oxygen gas for commercial and industrial applications, electroplating, extracting pure metals from alloys and so on.