4/08/13 Week 4 Sunday 2013 Home

Background Research - Galvanic Cells continued.

The salt bridge is important component in galvanic cells. As I talked about in the last diagram with Cu and Ag electrodes in solution, each container containing an electrode is called a half cell. The salt bridge is not only there to link the half cells, however balance out the change of electrons.

Cu(s) → Cu²⁺_(aq) + 2e^-_­

Ag⁺_(aq) + e^-_­ → Ag_(s)

If these two reactions were the only ones to occur in this galvanic cell, then the container containing Cu and NO₃ would end up with an excessive amount on positive ions due to the Cu ions being produced by the electrode reaction (metal to ion). Also the container containing Ag and NO₃ would end end up with an excessive amount of negative ions due to the electrode reaction (ion to metal). As a whole this migration and balance of electrons preserves neutrality in both half cells.

In summary the electrode process that releases electrons in called the anode and the electrode process absorbs electrons is called the cathode. The migration of negative electrons transfers from the cathode to the anode and the migration of positive ions transfers from the anode to the cathode.

A galvanic cell is an electron pump. It pumps electrons from the negative terminal into the external circuit and the back into the positive terminal due to the redox reaction occurring within the cell.

Anode: The electrode at which oxidation occurs

Cathode: The electrode at which reduction occurs.