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Galvanic Cells

From Chemistry to Electricity. Galvanic Cells. 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”. The Galvanic Reaction. Blue. Invisible.

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Galvanic Cells

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  1. From Chemistry to Electricity Galvanic Cells

  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 Blue Invisible Zn(s) + Cu2+(aq)→ Cu(s) + Zn2+(aq) Grey metal Red metal Reduction: Cu2+(aq) +2 e-→ Cu(s) Oxidation: Zn(s)→ Zn2+(aq) +2 e-

  4. The Galvanic Reaction in a Single Vessel Cu2+ Zn(s) Cu2+ Cu2+

  5. 2 e- Zn2+ The Galvanic Reaction in a Single Vessel Cu2+ Zn(s) Cu2+ Cu2+

  6. Zn2+ The Galvanic Reaction in a Single Vessel Cu2+ Zn(s) Cu(s) Cu2+

  7. 2 e- Zn2+ The Galvanic Reaction in Two Vessels Cu2+ Zn(s) Cu2+ Cu2+

  8. 2 e- Zn2+ The Galvanic Reaction in Two Vessels Conductor Cu2+ Zn(s) Cu2+ Cu2+

  9. Zn2+ The Galvanic Reaction in Two Vessels Conductor Cu(s) Zn(s) Cu2+ Cu2+

  10. Load Zn2+ Zn2+ Zn2+ The Galvanic Cell Current → Conductor Cu2+ Cu(s) Zn(s) Cathode Anode Cu2+ Cu2+ Oxidation happens at the anode Reduction happens at the 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. Load SO42- Na+ Zn2+ Zn2+ The Salt Bridge - - - - - + + + + + + Cu(s) Zn(s) Cu2+ Cu2+ Anode Cathode

  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. Write the half reactions. Take the half reactions to the lowest common multiple, and add them together to get the overall cell reaction. Zinc and Nickel b) Magnesium and Silver c) Silver and Gold d) Pop Cans and Pennies (Aluminium and Copper)

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