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14.1 cells.ppt

  1. 14.1 Cells and Batteries
  2. Origins of the Cell • Galvani (late 1700’s) observed a frog’s leg twitch when exposed to a current • Volta (early 1800’s) realized it was due to current flowing through electrolytes in body • Volta invented the first battery by connecting multiple electric cells together • Based on spontaneous redox rxtn’s it was able to produce a consistent current
  3. + + + – – – Cell design • “Cells” are containers of liquid with electrodes: • In “voltaic cells”, electricity is produced spontaneously from a redox reaction • In “electrolytic cells”, electricity is used to force chemicals to undergo a redox reaction Source or use of electricity Molten or aqueous chemicals Cell Electrode
  4. Voltaic Cell • also referred to as a “galvanic cell” • salt bridge or porous disk(cup) used to allow for unrelated ions to move to allow for balance of charge
  5. Cell Properties - driving force on electron to move them through the wire • electric potential difference is the energy difference per unit charge • depends on type of electrodes and electrolytes used in cells • electric current is rate of flow of charge in a circuit • power is the rate at which electrical energy is produced
  6. Cell Quantities Quantity Symbol Meter Units Charge Q C (coulombs) Current I ammeter A (ampere) Potential difference V voltmeter V (volt) Power P W (watt) Energy density J/kg
  7. Secondary Cells & Batteries  a battery is a group of galvanic cells connected in series  the potentials of the individual cells add to give the total battery potential  secondary cells can be recharged by adding electricity
  8. Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)
  9. Figure 6 A Common Dry Cell Battery (LSM 14.1C)
  10. Fuel Cells . . . voltaic cells where the reactants are continuously supplied. 2H2(g) + O2(g)  2H2O(l) anode: 2H2 + 4OH  4H2O + 4e cathode: 4e + O2 + 2H2O  4OH
  11. Figure 8 Schematic of the Hydrogen-Oxygen Fuel Cell (LSM 14.1C)
  12. Homework Textbook p. 614 #1-5 Textbook p. 619 #10-15 LSM 14.1 B,C,D