Inorganic and Applied Chemistry

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Inorganic and Applied Chemistry

Example 6- D:

Half-cell potentials

A galvanic cell contains a solution of ZnSO 4 connected through a porous wall (similar to the salt bridge

presented earlier) with a solution of HCl. In the zinc sulphate solution is placed a rod of zinc metal

connected to a platinum electrode placed in the hydrochloric acid solution. Simultaneously H 2 in gas form

is lead through the platinum electrode. Between the platinum and zinc electrode is placed a voltmeter. The

figure below presents the set-up of a galvanic cell.

Figure 6- 2: Galvanic cell

Schematic setup of a galvanic cell consisting of a zinc electrode/ZnSO 4 solution and a platinum

electrode/HCL solution.

As it may be seen from the figure above the cell potential for the entire cell is observed to be 0.76 volt

corresponding to the overall cell reaction:

2 H+(aq) + Zn(s)  Zn2+(aq) + H 2 (g)

For the given galvanic cell the anode part contains zinc metal electrode with Zn2+ and SO 4 2- ions in an

aqueous solution. The anode reaction is thereby given as:

Zn(s)  Zn2+(aq) + 2 e-

Through the anode reaction each zinc atom looses two electrons that migrate into the solution as Zn2+ ions.

Electrochemistry