1. Galvanic Cells From Chemistry to Electricity

2. Luigi Galvani Lived 1737-1798 in Bologna, Italy Physician During a dissection of a frog, his zinc scalpel and copper rod reacted to make the frog’s leg jump “Animal electricity”

3. The Galvanic Reaction Zn (s) + Cu 2+ (aq) → Cu (s) + Zn 2+ (aq) Oxidation: Zn (s) → Zn 2+ (aq) +2 e - Reduction: Cu 2+ (aq) +2 e - → Cu (s) Grey metal Red metal Blue Invisible

4. The Galvanic Reaction in a Single Vessel Zn(s)Cu 2+

5. The Galvanic Reaction in a Single Vessel Zn(s)2 e - Cu 2+ Zn 2+

6. The Galvanic Reaction in a Single Vessel Zn(s)Cu(s) Cu 2+ Zn 2+

7. The Galvanic Reaction in Two Vessels Cu 2+ Zn(s)2 e - Zn 2+

8. The Galvanic Reaction in Two Vessels Cu 2+ Zn(s)2 e - Conductor Zn 2+

9. The Galvanic Reaction in Two Vessels Cu 2+ Cu (s) Cu 2+ Zn(s) Conductor Zn 2+

10. The Galvanic Cell Cu 2+ Zn(s) Conductor Zn 2+ Cu (s) Cu 2+ Current → Load Oxidation happens at the anodeReduction happens at the cathode Anode Cathode

11. The Galvanic Cell A galvanic cell (also known as an electrochemical cell) is made from two dissimilar metals connected by a conductor and immersed in a solution that contains ions. The metal strips are called electrodes, and the solution is called an electrolyte. The anode is the electrode where oxidation occurs. It loses electrons, which travel through a circuit, and gradually decreases in mass. The anode is always the stronger reducing agent of the two metals. Anode and oxidation both start with vowels. The cathode is the electrode where reduction occurs. It gains electrons from the circuit, and gradually increases in mass. The cathode is always the weaker reducing agent of the two metals. Cathode and reduction both start with consonants. The electrons that travel through the circuit can be forced to do work by passing them through a load, such as a light bulb, buzzer, or diode. A galvanic cell changes chemical energy into electrical energy.

12. The Salt Bridge Cu 2+ Zn(s) Zn 2+ Cu (s) Cu 2+ Load AnodeCathode + + + + - SO 4 2- Na +

13. The Salt Bridge The salt bridge prevents positive charge from accumulating near the anode and negative charge from accumulating near the cathode. It contains both positive and negative ions that diffuse back and forth to keep the overall charges equal.

14. Practice Remember, you can make a galvanic cell out of any two metals, as long as they are far enough apart in the activity series. For each of the following pairs of metals: 1. State which will form the anode, and which will form the cathode. 1.Write the half reactions. 2.Take the half reactions to the lowest common multiple, and add them together to get the overall cell reaction. a)Zinc and Nickelb) Magnesium and Silver c) Silver and Goldd) Pop Cans and Pennies (Aluminium and Copper)