M

UCH OF CHEMISTRY INVOLVES SPECIES that have charge.

Electrons, cations, and anions are all charged particles that interact

chemically. Often electrons move from one chemical species to another to form

something new. These movements can be spontaneous, or they can be forced.

They can involve systems as simple as hydrogen and oxygen atoms, or as com-

plex as a million-peptide protein chain.

The presence and the value of discrete charges on chemical species intro-

duces a new aspect that we must consider, the fact that like charges repel and

opposite charges attract. In considering how charged particles interact, we have

to understand the work involved in moving charged particles together and

apart, and the energy required to perform that work. Energy, work—these are

concepts of thermodynamics. Therefore, our understanding of the chemistry

of electrically charged particles,electrochemistry,is based on thermodynamics.

Few people realize the widespread application of electrochemistry in modern

life. All batteries and fuel cells can be understood in terms of electrochemistry.

Any oxidation-reduction process can be considered in electrochemical terms.

Corrosion of metals, nonmetals, and ceramics is electrochemistry. Many vitally

important biochemical reactions involve the transfer of charge, which is electro-

chemistry. As the thermodynamics of charged particles are developed in this

chapter, realize that these principles are widely applicable to many systems and

reactions.

8.1 Synopsis

First, we will review the physics of charge interaction, which was understood

fairly early in the development of modern science. It is easy to relate thermo-

dynamic quantities, especially G, to the work and energy involved in moving

charged species. We can divide every electrochemical reaction into an oxida-

tion part, in which some species loses electrons, and a reduction part, in which

some species gains electrons. We will find that we can keep these parts sepa-

rate and combine them to generate new electrochemical processes.

Electrochemical reactions are dependent on the quantity of charged species

present, but because opposite charges attract each other, the simple specifica-

tion of concentration does not necessarily correlate with behavior. The concepts

8

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8.1 Synopsis

8.2 Charges

8.3 Energy and Work

8.4 Standard Potentials

8.5 Nonstandard Potentials and
Equilibrium Constants

8.6 Ions in Solution

8.7 Debye-Hückel Theory and
Ionic Solutions

8.8 Ionic Transport
and Conductance

8.9 Summary

Electrochemistry and

Ionic Solutions