Oxidation/Reduction & Batteries

Oxidation Combining with Oxygen – combustion Gives off energy Oxidation in the body – H 2 O and CO 2 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 + Br 2 → 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 So zinc is more active than copper So iron is more active than copper Is iron or zinc more active? – How do you tell? 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) During recharging the following also occurs: Is there a danger here?

H28 – C , , , 24, 26, 27, 29, , 53, 54