1. Oxidation and reduction reactions occur in many chemical systems. Examples include the rusting of iron, the action of bleach on stains, and the reactions of photosynthesis in the leaves of green plants. The study of these electrochemical changes is called electrochemistry. The applications of electrochemistry are widespread and examples include the production of liquid bleach and the use of batteries.

2. The electrolysis of water. When electricity is passed through a molten (melted) ionic compound or through a solution of an electrolyte, a chemical reaction occurs that we call electrolysis. A typical electrolysis apparatus, called an electrolysis cell, or electrolytic cell, is show below.

3. When electricity flows, chemical changes begin to happen. At the positive electrode, the anode, oxidation occurs as electrons are pulled from negatively charged ions. The direct current source pumps these electrons through the external electrical circuit to the negative electrode, the cathode. At the cathode, reduction takes place as the electrons are pushed onto positively charged ions.

4. REDuction at CAThode =RED CAT ANode for Oxidation =AN OX

5. In any apparatus in which an electrochemical reaction is taking place, the following definitions apply: The anode is the electrode at which oxidation occurs. The cathode is the electrode at which reduction occurs. The overall reaction that takes place in this electrolysis cell is called the cell reaction. 2Na + (l) + 2e - → 2Na(l) (cathode) 2Cl - (l) → Cl 2 (g) + 2e - (anode) _________________________________________________ 2Na + (l) + 2Cl - (l) + 2e - → 2Na(l) + Cl 2 (g) + 2e - (cell reaction)

6. Important!! In a electrolytic cell, electrical energy is used to produce a chemical change. That is, electrical work causes an otherwise nonspontaneous chemical reaction to occur.

7. The stoichiometry of electrolytic processes tell us how much chemical change occurs with the flow of a given current for a specified time. To use this information, we must be able to relate it to electrical measurements that can be made in the laboratory. The SI unit of electric current is the ampere (A) and the SI unit of charge is the coulomb (C). A coulomb is the amount of charge that passes by a given point in a wire when an electric current of one ampere flows for one second. 1 coulomb = 1 ampere x 1 second 1 C = 1 A ∙ s

8. For example, if a current of 4 A flows through a wire for 10 s, 40 C pass by a given point in the wire. (4 A) x (10 s) = 40 A ∙ s = 40 C Experimentally, it has been determined that 1 mol of electrons carries a charge of 96,485 C (round to 3 SF). 1 mol e - = 9.65 x 10 4 C In electrochemistry, 1 mol of electrons is called 1 faraday ; thus, 1 faraday = 9.65 x 10 4 C