Sample Introduction: The Voltaic Cell

by Dr. Deniz Korkmaz

The objective of this experiment is to construct a simple electrochemical cell and understand how it works.

Oxidation-reduction reactions involve a transfer of electrons from one species to another. Every oxidation-reduction reaction can be split into two half-reactions. Oxidation is the half reaction in which there is a loss of electrons by a species. Reduction is the half-reaction in which there is a gain of electrons by a species.

A voltaic, or galvanic, cell is an electrochemical cell in which a spontaneous reaction generates an electric current. A voltaic cell consists of two half cells that are electrically connected. Each half cell is the portion of an electrochemical cell in which a half-reaction takes place. Two half-cell reactions in this experiment will be:

Zn(s) --> Zn²⁺(aq) + 2e^- (oxidation half-reaction)
Cu²⁺(aq) + 2e^- --> Cu(s) (reduction half-reaction)

The electrode at which oxidation occurs is called the anode. The electrode at which oxidation occurs is called the cathode. The sum of the two half reactions

Zn(s) + Cu²⁺(aq) --> Zn²⁺(aq) + Cu(s)

is the net reaction that occurs in the voltaic cell; it is called the cell reaction (1).

References
1.Ebbing, D. D. General Chemistry, Fifth Edition; Houghton Mifflin: Boston; 1996.

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