Batteries and Fuel Cells

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Presentation transcript:

Batteries and Fuel Cells Pgs 655 - 658 Batteries and Fuel Cells

How can we use galvanic cells in everyday life? BATTERIES!! Take galvanic cells and make them easier to carry around and use!

All batteries require electrical potential: Li Rb K Cs Ba Sr Ca Na Mg Al Zn Cr Fe Ni Sn Pb Cu Hg Ag Au Most reactive What is electrical potential: The “pressure” on electrons to flow from one electrode to the other in a redox reaction Depends on the difference between the atoms being oxidized and reduced on the activity series Measured in volts Least reactive

Types of Batteries Lead Storage Batteries Dry Cell Batteries

Dry Cell Batteries Advantage of this type of battery: Small, efficient at producing energy, don’t contain a liquid Anode = Zinc case Solid Zn is oxidized at anode: Zn (s)  Zn2+ + 2e- Cathode = Graphite rod NH4+ and MnO2 is reduced Used in calculators, watches, flashlights What makes an alkaline battery different? Last longer because the Zn doesn’t corrode as quickly in the basic environment!

How does our lab from Friday link to corrosion? Corrosion is the process of returning metals to their natural state It’s a REDOX reaction!! Fe (s) + O2 (g)  Fe2O3 (s)

LOTS of metals corrode, but not all of them corrode to the same extent: Ex  Aluminum!! Aluminum will be oxidized by the air Al (s) + O2 (g)  Al2O3 (s) A thin layer of Al2O3 will cover the metal and protect it from further corrosion

How can we protect these metals from corrosion? The Mg will react instead of the iron…but why???

Lead Storage Batteries Advantages of this type of battery: Can work for several years in extreme temperatures Provides a lot of voltage (12 V) for its size RECHARGE themselves!! Where do we use lead storage batteries? IN CARS!!!

Lead Storage Batteries Anode = metal lead Cathode = lead (IV) oxide coated onto lead grids Solution = H2SO4 Anode and cathode are separated, so the e- move through a wire that provides an electric current to run the car Reaction  Pb + H2SO4  PbSO4 + 2H+ + 2e- Reaction  PbO2 + 2e- + 2H+  PbSO4 + 2H2O

So what about hydrogen fuel cells? Fuel cells: galvanic cells in which a fuel substance undergoes oxidation which creates energy Don’t have to be re-charged Can be created so that no air pollutants are produced Used to run the Apollo missions Trying to find a way to use them in cars!

Hydrogen Fuel Cells Cathode compartment has oxygen gas Anode compartment has hydrogen gas Middle compartment a membrane that allows H+ to move to O2 Oxidation: 2H2 (g) +  4H+ + 4e- Reduction: O2 (g) + 4H+ +4e-  2H2O (l) Overall: 2H2 (g) + O2 (g)  2H2O (l)

Hydrogen Fuel Cells and Cars http://www.chevrolet.com/fuelcell/ Show fuel cell Nova science now video