Lecture2310c

Lecture2310c - Chemistry 83 Adverse Effects of Current...

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Chemistry 83 11/30/10 1 Adverse Effects of Current Technologies on Atmosphere International Agreements on: Acid Rain Climate Change Ozone Depletion Tro, page 327 [H + ] = 10 -pH Increasingly Acidic Increasingly Basic pH = -log 10 [H + ] or [H + ] = 10 -pH [H + ] http://www.uvprocess.com/product.asp?code=PH+++++++B Acidity of an solution(aq) is quantified by pH
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Chemistry 83 11/30/10 2 pH of common substances (average) http://wpcontent.answers.com/wikipedia/commons/thumb/4/46/PH_scale.png/350px-PH_scale.png Pure water has a pH = 7 Natural rainwater has a pH 5.6 due to H 2 CO 3 Acid rain has a pH < 5.6 due to presence of additional acid(s): HNO 3 and/or H 2 SO 4 . http://nadp.sws.uiuc.edu/isopleths/maps1999/phfeld.giF All rain falling on US is acidic (pH < 7), but only rain having pH < 5.6 is defined as acid rain Record low pH
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Chemistry 83 11/30/10 3 Acid rain is defned as rain having a pH < 5.6 • pH oF rain depends on presence/absence oF three acid anhydrides in air: CO 2 , NO 2 , and SO 3 • These acid anhydrides can react with rain water to produce acids: H 2 CO 3 , HNO 3 , and H 2 SO 4 ; respectively • Natural rain contains only H 2 CO 3 and has an acidity oF pH 5.6 • Acid rain contains H 2 CO 3 plus HNO 3 and/ or H 2 SO 4 and has a pH < 5.6 Buell/Girard, Chemistry, Prentice Hall, NJ, 1994, 231 Source of acid rain is combustion of fossil fuels
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Chemistry 83 11/30/10 4 Figure. Marble tombstone that has been exposed to acid rain in England since 1817. Raven et al, Environment, Saunders, NY, 1995, 450 Acid rain dissolves marble statues and monuments: CaCO 3 + H + Ca 2+ + HCO 3 - Adverse effect of acid rain on materials CaCO 3 + H + Ca 2+ + HCO 3 - Limestone reacts with acids: Unprotected areas: Al 2 Si 2 O 5 (OH) 4 + 6 H + 2 Al 3+ + 2 SiO 2 + 5 H 2 O (Clay) (toxic) Adverse effects of acid rain on lithosphere and hydrosphere are decreased by limestone Buell/Girard, Chemistry, Prentice Hall, NJ, 1994, 232 Figure. Uncolored areas are protected by natural limestone deposits.
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Chemistry 83 11/30/10 5 Schwartz et al, Chemistry in Context, ACS, DC, 1994, 171 Buell/Girard, Chemistry, Prentice Hall, NJ, 1994, 232 Acid rain releases toxic Al 3+ ions that kill trees and fish Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 727 CaCO 3 + H + Ca 2+ + HCO 3 - Remediation: limestone can be added to soil (called end-of-pipe treatment)
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Chemistry 83 11/30/10 6 http://news.bbc.co.uk/2/hi/science/nature/4468076.stm S can be removed from coal before combustion (called source reduction treatment) (FeS 2 ) Effective but is costly in energy and money. Clean Air Act amendments (1990) deal with acid rain by
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This note was uploaded on 12/19/2010 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Lecture2310c - Chemistry 83 Adverse Effects of Current...

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