Potentials, in galvanic cells

Metallic copper precipitates spontaneously, therefore, the reaction according to the equilibrium condition in eqn. (5.7) necessarily involves a decrease of free energy (AG < 0). The reaction is qualitatively explained in the following way Zinc atoms at the surface of the electrode show a certain tendency to dissolve into ions Zn++(aq) and leave 2 free electrons in the electrode metal. The corresponding tendency to dissolve is less for copper atoms. Copper ions Cu++ in the solution, therefore, take up the liberated electrons and are reduced to Cu(s) that is precipitated on the electrode. In the following, we shall see how this phenomenon is decisive to the build-up of an electrochemical potential in galvanic cells. 

The galvanic cell with Zn Cu electrodes described here is called a Daniell cell, named after the English physicist. J.F. Daniell (1836). The Daniell cell illustrates the underlying principle for build-up of the electrochemical potentials in galvanic cells. Similar potentials can arise locally in moisture exposed metal members in building structures and cause electrolytic corrosion. In the following sections, therefore, we shall look further into this phenomenon. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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