14.1 Cells and Batteries

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

+ + + – – – 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

Voltaic Cell also referred to as a “galvanic 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 chargesalt bridge or porous disk(cup) used to allow for unrelated ions to move to allow for balance of charge

Cell Properties - driving force on electron to move them through the wire electric potential difference is the energy difference per unit chargeelectric potential difference is the energy difference per unit charge depends on type of electrodes and electrolytes used in cellsdepends on type of electrodes and electrolytes used in cells electric current is rate of flow of charge in a circuitelectric current is rate of flow of charge in a circuit power is the rate at which electrical energy is producedpower is the rate at which electrical energy is produced

Cell Quantities QuantitySymbolMeterUnits ChargeQC (coulombs) CurrentIammeterA (ampere) Potential difference VvoltmeterV (volt) PowerPW (watt) Energy density J/kg

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

Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)

Figure 6 A Common Dry Cell Battery (LSM 14.1C)

Fuel Cells...voltaic cells where the reactants are continuously supplied. 2H 2 (g) + O 2 (g)  2H 2 O(l) anode: 2H 2 + 4OH   4H 2 O + 4e  cathode: 4e  + O 2 + 2H 2 O  4OH 

Figure 8 Schematic of the Hydrogen-Oxygen Fuel Cell (LSM 14.1C)

Homework Textbook p. 614 #1-5 Textbook p. 619 #10-15 LSM 14.1 B,C,D