1. Electrochemical Cells - producing an electric current with a redox reaction

2. The connection between electricity and chemical reactions was discovered by Galvani and Volta, 2 Italian chemists. Electrochemical cells are also known as galvanic cells or voltaic cells in their honor.

3. Consider the reaction: Zn (s) + Cu 2+ (aq)  Zn 2+ (aq) + Cu (s) Zn is oxidized and is the reducing agent. Cu 2+ is reduced and is the oxidizing agent. When a strip of Zn metal is dipped into a solution of copper ions, the spontaneous reaction results in a direct transfer of electrons from the Zn to the copper. This, however, does not generate any electricity.

4. When the two half reactions are placed in separate containers and connected with a wire, an electric current can be produced. Electricity is defined as the flow of electrons.

6. The oxidation half reaction occurs in the beaker on the left. The reduction half reaction occurs in the beaker on the right. Electrons are pulled by the oxidizing agent, so electrons will flow thru the wire from the reducing agent to the oxidizing agent.

8. As Zn metal loses electrons, positive zinc ions are produced. The electrode where oxidation takes place is called the anode. Think “anox”

10. As electrons are gained, positive copper ions turn into copper metal. The electrode where reduction takes place is called the cathode. Think “redcat”

12. Purpose of the Salt Bridge As the redox rxn proceeds, over time a positive charge would build up in the left side as Zn 2+ ions are formed and a negative charge would build up in the right side as Cu 2+ are reduced, leaving behind SO 4 2-. The salt bridge allows ions to travel back and forth to keep the charge balanced.

13. Anions travel toward the anode. Cations travel toward the cathode. Without the salt bridge, the circuit would not be complete and an electric current would not flow through the wire.