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7. Electrochemistry eLearn.Punjab

A galvanic cell consists of two cells, each called as half-cell, connected electrically by a salt bridge.
In each of the half-cell, an electrode is dipped in 1 M solution of its own salt and connected through
a wire to an external circuit. Figure.7.3 shows a typical galvanic cell.
The left half-cell consists of an electrode of zinc metal dipped in 1 M solution of zinc sulphate. The
right half-cell is a copper electrode dipped in I M solution of copper sulphate. Salt bridge is a U
shaped glass tube. It consists of saturated solution of strong electrolyte supported in a jelly type
material. The ends of the U tube are sealed with a porous material like glass wool. The function of
the salt bridge is to keep the solutions of two half-cells neutral by providing a pathway for migration
of ions.
7.5.3.2 Working of the Cell

The Zn metal has tendency to lose electrons more readily than copper. As a result oxidation takes
place at Zn-electrode. The electrons flow from Zn-electrode through the external wire in a circuit
to copper electrode. These electrons are gained by the copper ions of the solution and copper
atoms deposit at the electrode. The respective oxidation and reduction processes going on at two
electrodes are as follows:
Half-cell reaction at anode (oxidation)

Zn(s) → Zn2+(aq) + 2e_

Half-cell reaction at cathode (reduction)

Cu2+(aq) + 2e_ → Cu(s)

Overall galvanic reaction is the sum of these two half-cell reactions

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)

As a result of redox reaction, electric current is produced. The batteries which are used for starting
automobiles, running calculators and toys and to lit the bulbs work on the same principle.

Animation 7.7: Galvanic cell Animation7.8: Electrolytic cell
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