BATTERIES AND FUEL CELLSPgs 655 - 658

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: 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

Li Rb

KCsBaSrCaNaMgAlZnCrFeNiSnPbCuHgAgAu

Most reactive

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 cathodeare separated, so thee- move through a wirethat provides an electric current to runthe car

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