The Foundations of Chemistry

• Compare various voltaic cells to determine the relative strengths of oxidizing and
  reducing agents


• Interpret standard reduction potentials


• Use standard reduction potentials, E^0 , to calculate the potential of a standard voltaic
  cell, E^0 cell


• Use standard reduction potentials to identify the cathode and the anode in a standard
  cell


• Use standard reduction potentials to predict the spontaneity of a redox reaction


• Use standard reduction potentials to identify oxidizing and reducing agents in a cell or
  in a redox reaction


• Describe some corrosion processes and some methods for preventing corrosion


• Use the Nernst equation to relate electrode potentials and cell potentials to different
  concentrations and partial pressures


• Relate the standard cell potential (E^0 cell) to the standard Gibbs free energy change
  (
  G^0 ) and the equilibrium constant (K)


• Distinguish between primary and secondary voltaic cells


• Describe the compositions and reactions of some useful primary and secondary cells
  (batteries)


• Describe the electrochemical processes involved in discharging and recharging a lead
  storage (automobile) battery

EE

lectrochemistry deals with the chemical changes produced by electric current and

with the production of electricity by chemical reactions. Many metals are purified

or are plated onto jewelry by electrochemical methods. Digital watches, automo-

bile starters, calculators, and pacemakers are just a few devices that depend on

electrochemically produced power. Corrosion of metals is an electrochemical process.

We learn much about chemical reactions from the study of electrochemistry. The

amount of electrical energy consumed or produced can be measured quite accurately. All

electrochemical reactions involve the transfer of electrons and are therefore oxidation–

reductionreactions. The sites of oxidation and reduction are separated physically so that

oxidation occurs at one location, and reduction occurs at the other. Electrochemical

processes require some method of introducing a stream of electrons into a reacting chem-

ical system and some means of withdrawing electrons. In most applications the reacting

system is contained in a cell,and an electric current enters or exits by electrodes.

We classify electrochemical cells into two types.

1. Electrolytic cellsare those in which electrical energy from an external source causes
   nonspontaneouschemical reactions to occur.


2. Voltaic cellsare those in which spontaneouschemical reactions produce electricity
   and supply it to an external circuit.

You should review oxidation–

reduction (redox) reactions in

text Section 4-5. See the Saunders

Interactive General Chemistry CD-ROM,

Screen 21.2, Redox Reactions.

See the Saunders Interactive

General Chemistry CD-ROM,

Screen 21.4, Electrochemical Cells.