23.3. Electrolysis http://www.ck12.org
23.3 Electrolysis
Lesson Objectives
- Distinguish between voltaic and electrolytic cells.
- Describe a Down’s cell, and identify the products of the electrolysis of molten sodium chloride.
- Describe the reactions that occur during the electrolysis of water.
- Identify the products that would be generated during the electrolysis of an aqueous solution of sodium chloride.
- Describe the process of electroplating.
Lesson Vocabulary
- electrolysis
- electrolytic cell
- electroplating
Check Your Understanding
Recalling Prior Knowledge
- What half-reactions occur at the anode and cathode of an electrochemical cell?
- How can you tell from a standard cell potential whether an electrochemical reaction is spontaneous or non-
spontaneous under standard conditions?
A nonspontaneous reaction is one in which the reactants are favored over the products under a given set of reaction
conditions. However, if a chemical system is supplied with energy from an external source, it is possible to drive a
reaction in the nonspontaneous direction. In this lesson, you will learn about this type of electrochemical process,
which is called electrolysis.
Electrolytic Cells
A voltaic cell uses a spontaneous redox reaction to generate an electric current. It is also possible to do the
opposite. When an external source of direct current is applied to an electrochemical cell, a reaction that is normally
nonspontaneous can be forced to proceed.Electrolysisisthe process in which electrical energy is used to cause a
nonspontaneous chemical reaction to occur. Electrolysis is responsible for the metal coatings that appear on many
everyday objects, such as gold-plated or silver-plated jewelry and chrome-plated car bumpers.
Anelectrolytic cellisthe apparatus used for carrying out an electrolysis reaction. The figure below (Figure23.7)
shows an electrolytic cell composed of Zn|Zn^2 +and Cu|Cu^2 +half-cells.