http://www.ck12.org Chapter 23. Electrochemistry
23.3 Electrolysis
Lesson Objectives
- Define electrolysis.
- Describe the use of electrolysis in the purification of sodium.
- Understand the basics of the process of refining aluminum.
Lesson Vocabulary
- electrolysis: The process in which electrical energy is used to cause a nonspontaneous chemical reaction to
occur. - electrolytic cell: The apparatus used for carrying out an electrolysis reaction; consists of an electrolyte to
carry charge and two electrodes. - electrometallurgy: A technique of extracting and purifying metals from their ores through use of electrolysis.
Check Your Understanding
Recalling Prior Knowledge
- Review the activity series and the standard reduction potential information to predict how metals will interact
with one another.
Electrolysis
A galvanic 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.Electrolysisis the 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 cellis the apparatus used for carrying out an electrolysis reaction.Figure23.11 shows an electrolytic
cell composed of Zn|Zn^2 +and Cu|Cu^2 +half-cells.
Recall that in the last section, this same pair of half-cells was used as an example of a voltaic cell. In the spontaneous
direction, Zn metal is oxidized to Zn^2 +ions while Cu^2 +ions are reduced to Cu metal. In a voltaic cell, the zinc
electrode would be the anode and the copper electrode would be the cathode. However, when the same half-cells are
connected to a battery via an external wire, the reaction is forced to run in the opposite direction. The zinc electrode
is now the cathode and the copper electrode is the anode.