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10Electron Transfer
Reactions*Oxidation & reduction
(revisited)
Today’s lecture is brought to you by the number…
2
Geez….almost all reactions are this!
Hindenburg: oxidation of hydrogen by oxygen, reduction of oxygen by
hydrogen. http://www.youtube.com/watch?v=CgWHbpMVQ1U http://www.youtube.com/watch?v=xiAT9xvTVKI&feature=related
2H2 4H+ + 4e- Oxidation Half Rxn 4e- + O2 2O2- Reduction Half Rxn_____________________
2H2 + O2 4H+ + 2O2- 2H2O
RedOx means Reduction and Oxidation; They go hand-in-hand. RedOx means Reduction and Oxidation; They go hand-in-hand.
Reduction OxidationLose oxygen Gain oxygen
Gain hydrogen Lose hydrogen
Gain electrons Lose electrons
This is the “smoke on the water” reaction we saw on
video. 2Na + 2H2O 2Na+ + H2 + 2OH-
Na was oxidized: Na Na+ + e- (electron lost) H was reduced: lost oxygen O no change: lost H but gained e-
Remember…we can actually run this reaction by dumping some sodium into water.
ReDox in organic systems is tricky.
2 CH3OH 2 CH2O + H2
C: ???H: ???H: ???O: ???
This one is very tricky (and related to “butter vs.
margarine”)CH3CH2CH2CH=CHCH2CH3 + H2
CH3CH2CH2CH-CHCH2CH3 H H
C ?????H ?????
Not-so-Secret Agents: all part of the semantics nightmare that is
RedOxSomething that promotes reduction: reducing agent
Example: K, Na, H, LiAlH4
Something that promotes oxidation: oxidizing agent
Example, O, F, Br, K2Cr2O7
Main Applications of RedOxRecovery of metals from ores
Corrosion
Prevention of corrosion
Batteries
And the sons of Pullman porters & the sons of engineersRide their fathers' magic carpet made of steel
Mothers with their babes asleep, rockin' to the gentle beatAnd the rhythm of the rails is all they feel
City of New Orleans—Steve Goodman
Steel!
A country that makes stuff makes steel.
Reducing Iron Ore to Make Steel:
from rust to riches2 Fe2O3 + 3C 4 Fe + 3CO2
Rusti.e., ore
FromCoal
How steel is really made: http://www.sidmar.be/CONTENT/2c.htm
RedOx contributes to our geography, history and
economics.
COAL
IRON ORE
CARS
Why a steel factory in Louisiana?
Electro-reduction for aluminum production takes much energy.
2Al2O3 4Al + 3O2
Electrons returned
Electrons supplied
Power Plant
http://www.ocrwm.doe.gov/youth/images/powerplant.jpg
http://www.epa.gov/highgwp/aluminum-pfc/images/exhibit3.gif
http://www.terragalleria.com/images/us-ca/usca10035.jpeg
Hydroelectric Power
Hydroelectric Power
Aircraft Industry
Aluminum production affects/has affected geography, too.
Why do we recycle aluminum?
http://www.recycle.novelis.com/Recycle/EN/Kids/Fun+Facts/Many+Lives+of+the+Aluminum+Can/
Corrosion is the auto restorer’s enemy!
2 Fe 2 Fe+2 + 4 e-
4e- + 2H2O + O2 4OH-Electrons travel down nail
Someday, someday…
Rust on my Barracuda
http://cardesign.homestead.com/BaraMtn72.jpg
Batteries! What if we could trap those electrons, make
‘em do some work before the reduction step?
ENR vs XOM
Fuel Cells—a quick intro to why we need chemistry and chemical
engineers. Honda FCX fuel cell concept at ~100 mph on a test track.It goes 354 miles without refueling with hydrogen.
Images from treehugger.com (no kidding, that’s the site!)
How soon? Soon!http://www.youtube.com/watch?v=y3VtrzcKQk Hey…where are we gonna get the hydrogen?
We are reliant on foreign oil. http://www.worldfuturefund.org/wffmaster/Charts-HTML/Energy/u
s-oil.htm
U.S. oilimports as a percentageof consumption
But maybe not forever, thanks (?) to fracking to recover natural gas.
http://www.saudi-us-relations.org/newsletter/saudi-relations-12.html
http://ils.unc.edu/~lanck/images/Roosevelt.jpg
Let’s go to the fabulous HowStuffWorks site to see how
Fuel Cells work. Clickable: http://auto.howstuffworks.com/fuel-cell3.htm http://auto.howstuffworks.com/fuel-cell3.htm Pasteable: http://auto.howstuffworks.com/fuel-cell3.htm
So, what are the technical challenges? The hydrogen has to come from somewhere. Transport of the protons across the polymer membrane requires the membrane be hydrated and liquid. The membrane (think of it as a sulfonated teflon) is expensive and can be damaged or fouled.The electrodes can become fouled. Expensive metals are used to catalyze the reaction.
About one billion dollars has been spent so far. Is that a
lot? Approx 5% of the budget of one of America’s poorest states (LA).
Twelve hundred times less than estimated project costs of a certain military intervention in the Mideast.
(N.Y. Times estimate $1200 Billion)Ford and Airstream Concept Fuel Cell Minivan
Don’t believe everything you see!
http://www.allthingsbeautiful.com/all_things_beautiful/images/churchill_roosevelt_stalin.jpg
I still haven’t said where the H2 comes from. Look at this Los Angeles Solar
Parking lot, though.
At the other end of I-10 is a windfarm.
Hybrid Vehicles: operate on gasoline with a battery storage system.
RedOx Chemistry Galore
“The car Detroit wants you to believe cannot be built.”But is that fair???
Hybrid Locomotive: GM is great at this stuff.
Chevy Volt is now selling….slowly.
Cool Fuel Cell Links
How Stuff Works Link: http://science.howstuffworks.com/
fuel-cell1.htm http://science.howstuffworks.com/
framed.htm?parent=fuel-cell.htm&url=http://education.lanl.gov/resources/h2/gottesfeld/education.html
“Maybe I should invest in fuel cells.”
P. Russo, 1999