Transcript Fossil Fuels - Snow College

Oxidation/Reduction
& Batteries
Oxidation
•
•
•
•
Combining with Oxygen – combustion
Gives off energy
Oxidation in the body – H2O and CO2
Oxidation in an engine – above plus CO
and NOx’s
– Degree of oxidation – CO not totally oxidized
• Rusting of Iron
Oxidation
• Gaining oxygen or loosing electrons
2Na + Br2 → 2Na+ + 2Br- → 2NaBr
• Which looses electrons?
• F, Cl, Br, I are common oxidizing agents
• Oxidizing agents cause other substances
to be oxidized
Reduction
• Oxidation/Reduction like Acid/Base
– Always in pairs
– Instead of exchanging protons, exchanging:
• Electrons
• Oxygen
• Losing oxygen or gaining electrons
– Memory table
• Metal ores are oxidized metals, must be
reduced
Reduction
• Reducing agents cause other substances
to be reduced.
• What are anti-oxidants?
Reduction
• Anti-oxidants are electron donors
– Reduce potential oxidizing agents
• Free radicals – unpaired electron wants another
• Takes electrons – oxidizes
• Vitamins A, C, and E
Strengths of Redox Agents
Zn(s) + Cu2+
(aq)
Zn2+
+ Cu(s)
(aq)
• So zinc is more active than copper
Fe(s) + Cu 2+
(aq)
Fe2+
+ Cu(s)
(aq)
• So iron is more active than copper
• Is iron or zinc more active? – How do you
tell?
2+
2+
Zn(s) + Fe(aq)
Zn(aq) + Fe(s)
• The more active a metal is, the more it
wants to be oxidized or ionized.
Batteries
• Based on activity of metals, etc.
– Something oxidized that wants to be reduced
– Something reduced that wants to be oxidized
Batteries
• Based on activity of metals, etc.
– Something oxidized that wants to be reduced
– Something reduced that wants to be oxidized
• Store electricity as chemical energy
• Primary batteries – cannot be recharged
– Dry cells, alkaline, lithium
• Secondary batteries – rechargeable
– NiCad, NiMH, Lead acid, rechargeable
alkaline, Lithium ion
• Which is better for the environment?
Lead Acid Batteries
(car batteries)
Pb( s)+PbO2( s)+2H2SO4( aq)
2PbSO4( s) + 2H2O + e-
•During recharging the following also occurs:
2H2O
2H2 + O2
•Is there a danger here?
H28 – C12
• 1 - 5, 8 - 10, 13 - 16, 24, 26, 27, 29, 47 51, 53, 54