Electrochemistry is a science that offers the solution to our energy needs. It is the study
of oxidation-reduction reactions that deals with the relationship between chemical energy
and electrical energy. This process is carried out in an electrochemical cell that consists
of electrodes dipped into an electrolyte and in which chemical reaction either generates or
uses electric current. There are two types of electrochemical cells, labeled differently
based on their tasks:
(a) Chemical energy into electrical energy: This process is carried out in voltaic
or galvanic cell that is nothing but an electrochemical cell in which a spontaneous
chemical reaction generates an electric current.
(b) Electrical energy into chemical energy: This process is carried out in an
electrolytic cell that is also an electrochemical cell in which an electric current is used to
drive an otherwise nonspontaneous chemical reaction. This process is known as
electrolysis.
Both processes are very important industrially and make our lives more comfortable and
enjoyable.
Galvanic Cells
Galvanic cell also known as voltaic cell (named after Italian scientists Luigi Galvani and
Alessandro Volta) is a device in which redox reactions are carried out to generate
electrical energy from chemical energy from spontaneous reactions. To illustrate the
concept of galvanic cell, consider the following example of piece of zinc (Zn) metal
placed in a solution of copper sulfate (CuSO4), where Zn is oxidized Zn+2 and Cu+2 is
reduced to Cu.
This process is described by the following redox equation:
Zn(s) + Cu+2(aq) Æ Zn+(aq) + Cu(s)
The electrons are directly transferred from the metallic Zn to Cu+ 2 ions in solution. Thus
the electrons appear and disappear in solution itself, which are of little use. However, if
we take the electrons out of the solution and pass them through the external wire and
bring them back to solution, then in essence we are passing the current in the external
wire that can be utilized for useful purpose. In order to do that the metallic Zn must be
1
