CHEM20204_exam

CHEM20204_exam - CHEM 20204-01: Environmental Chemistry...

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Final Exam Study Guide Ideal Gas Law • PV = nRT P = pressure (atm) of the gas V = volume (L) of the gas n = number of moles of the gas T = temperature (K) of the gas R = universal gas constant = 0.082 L · atm / mol · K = 8.314 J / K Energy of a Photon • E = = hc / λ = (119,627 kJ · nm / mol) / λ = (1240 nm · eV) / λ E = energy (kJ, eV) λ = wavelength (nm) Electromagnetic Spectrum ultraviolet (UV) light [50-400 nm] → visible light [400-750 nm] → infrared (IR) light [750-4,000 nm] UV-C [200-280 nm] → UV-B [280-320 nm] → UV-A [320-400 nm] Hess’s Law and Enthalpy Change H ° = ∑∆ H f ° (products) – ∑∆ H f ° (reactants) H f ° = enthalpy of formation (kJ / mol) Ozone Chemistry Mechanism I : 2 3 2 2 2 2 3 . . 2 3 2 2 3 O 2 O O O NO O NO O NO O NO O 2 O O O X O XO O XO O X + + + + + → + + + + + g e Mechanism II : 2 3 2 2 3 2 3 . . 2 3 2 2 3 2 3 3O O 2 O Br Cl BrO ClO O BrO O Br O ClO O Cl 3O O 2 O X X O X XO O O X O X O XO O X + + + + + + + → + + + + + + + g e • The total amount of atmospheric ozone that lies over a given point on earth is measured in terms of Dobson units (DU), where 1 DU is equivalent to a 0.01-mm thickness of pure ozone at the density it would possess if it were brought to ground-level pressure of 1 atm and 273 K temperature. • The ozone layer absorbs, or filters, UV-B light and protects against harmful ultraviolet radiation. The actual destruction of ozone is more than predicted due to ozone-depleting substances , such as CFC’s, HCFC’s, HBFC’s, and halons. The Montreal Protocol in 1987 sought to limit the use of CFC’s. Active forms of chlorine : Cl, ClO Inactive forms of chlorine : HCl, ClONO 2 Acid Rain • Rain water is naturally acidic due to the dissolution of carbon dioxide. Sources of acid rain : H 2 SO 4 (from SO x ) and HNO 3 (from NO x ) Effects of acid rain damage : disappearance of forests, acidification of lakes and death of aquatic organisms, leaching of aluminum, destruction of monuments Chlorofluorocarbons • CFC – chlorofluorocarbon CFC-113 113 + 90 = 203 2 C, 0 H, 3 F C 2 F 3 Cl 3 • HFC – hydrofluorocarbon HFC-134b 134 + 90 = 224 2 C, 2 H, 4 F C 2 H 2 F 4 • HCFC – hydrochlorofluorocarbon
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This note was uploaded on 02/25/2012 for the course CHEM 4385 taught by Professor Staff during the Fall '11 term at Texas State.

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CHEM20204_exam - CHEM 20204-01: Environmental Chemistry...

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