Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
205
Electrochemistry
Electrochemistry
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 20
20.1 Voltaic Cells
Electrochemistry is the study of processes by which chemical energy
is converted to electrical energy and vice versa. This branch of
chemistry has numerous applications in today’s increasingly technological world, such as for batteries, electronic components, and
commercial electroplating.
In Chapter 20, you learned that electrons are transferred between
atoms in oxidation–reduction (redox) reactions. Consider the redox
reaction represented by the following net ionic equation.
Ni(s) ϩ Cu 2ϩ (aq) 0 Ni 2ϩ (aq) ϩ Cu(s)
In this reaction, nickel metal is oxidized to Ni 2ϩ ions, and Cu 2ϩ ions
are reduced to copper metal. The half-reactions are as follows.
Ni(s) 0 Ni 2ϩ (aq) ϩ 2e Ϫ (oxidation)
Cu 2ϩ (aq) ϩ 2e Ϫ 0 Cu(s) (reduction)
This redox reaction can be used to generate an electric current by
using an electrochemical cell, an apparatus that uses a redox reaction to produce electrical energy (voltaic cell) or uses electrical
energy to cause a chemical reaction (electrolytic cell). The voltaic
cell for this reaction begins with a strip of nickel metal in an aqueous solution of Ni 2ϩ ions and a strip of copper metal in a solution of
Cu 2ϩ ions. Then, a metal-conducting wire is attached to the metal
strips in the solutions. Finally, a salt bridge connects the two solutions. A salt bridge is usually a tube containing a conducting
solution of a soluble salt, held in place by a plug, such as cotton or
agar gel. The salt bridge allows the passage of ions into the two
solutions but prevents the solutions from mixing.
When the voltaic cell is complete, the redox reaction proceeds.
Electrons flow through the wire from the nickel strip to the copper
strip, creating an electric current. The nickel strip is oxidized to Ni 2ϩ
ions, while the Cu 2ϩ ions in the other solution are reduced to copper
metal, which plates out on the copper strip. Ions flow from the salt
bridge into the two solutions to maintain the balance of charges.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
205
Electrochemistry
Electrochemistry
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 20
20.1 Voltaic Cells
Electrochemistry is the study of processes by which chemical energy
is converted to electrical energy and vice versa. This branch of
chemistry has numerous applications in today’s increasingly technological world, such as for batteries, electronic components, and
commercial electroplating.
In Chapter 20, you learned that electrons are transferred between
atoms in oxidation–reduction (redox) reactions. Consider the redox
reaction represented by the following net ionic equation.
Ni(s) ϩ Cu 2ϩ (aq) 0 Ni 2ϩ (aq) ϩ Cu(s)
In this reaction, nickel metal is oxidized to Ni 2ϩ ions, and Cu 2ϩ ions
are reduced to copper metal. The half-reactions are as follows.
Ni(s) 0 Ni 2ϩ (aq) ϩ 2e Ϫ (oxidation)
Cu 2ϩ (aq) ϩ 2e Ϫ 0 Cu(s) (reduction)
This redox reaction can be used to generate an electric current by
using an electrochemical cell, an apparatus that uses a redox reaction to produce electrical energy (voltaic cell) or uses electrical
energy to cause a chemical reaction (electrolytic cell). The voltaic
cell for this reaction begins with a strip of nickel metal in an aqueous solution of Ni 2ϩ ions and a strip of copper metal in a solution of
Cu 2ϩ ions. Then, a metal-conducting wire is attached to the metal
strips in the solutions. Finally, a salt bridge connects the two solutions. A salt bridge is usually a tube containing a conducting
solution of a soluble salt, held in place by a plug, such as cotton or
agar gel. The salt bridge allows the passage of ions into the two
solutions but prevents the solutions from mixing.
When the voltaic cell is complete, the redox reaction proceeds.
Electrons flow through the wire from the nickel strip to the copper
strip, creating an electric current. The nickel strip is oxidized to Ni 2ϩ
ions, while the Cu 2ϩ ions in the other solution are reduced to copper
metal, which plates out on the copper strip. Ions flow from the salt
bridge into the two solutions to maintain the balance of charges.