1. Galvanic Cells Electrochem part II

2. Voltaic Cells In spontaneous oxidation- reduction (redox) reactions, electrons are transferred and energy is released.

3. Galvanic Cell We can use that energy to do work if we make the electrons flow through an external device. We call such a setup a galvanic cell.

4. Galvanic Cells Once even one electron flows from the anode to the cathode, the charges in each beaker would not be balanced and the flow of electrons would stop.

5. We left the galvanic cell The galvanic cell as previously drawn had a brief current that quickly died. Why did it die? There was a build up of charges on either side of the cell that required too much energy to overcome.

6. To Solve the problem… The solutions must be connected so that ions can flow to keep the net charge in each compartment neutral. There are two methods: –A porous disc. –A salt bridge.

7. Porous Disc: A connection between the two compartments which allows ions to flow, but the solutions do not mix.

8. Salt Bridge: A tube connecting two compartments. The tube is filled with an electrolyte such as KNO 3 or other spectator ions.

9. The Galvanic Cells A typical cell looks like this. The oxidation occurs at the anode. The reduction occurs at the cathode.

10. The essentials of a Galvanic Cell A device in which chemical Energy is changed into electrical energy. The opposite process in which electrical energy drives a chemical reaction is called ELECTROLYSIS.

11. In the cell, then, electrons leave the anode and flow through the wire to the cathode. As the electrons leave the anode, the cations formed dissolve into the solution in the anode compartment.

12. As the electrons reach the cathode, cations in the cathode are attracted to the now negative cathode. The electrons are taken by the cation, and the neutral metal is deposited on the cathode.

13. Electromotive Force (emf) Water only spontaneously flows one way in a waterfall. Likewise, electrons only spontaneously flow one way in a redox reaction— from higher to lower potential energy.

14. Electromotive Force (emf) The potential difference between the anode and cathode in a cell is called the electromotive force (emf). It is also called the cell potential and is designated E cell.

15. Cell Potential Cell potential is measured in volts (V). 1 V = 1 JCJC

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