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Atmosphere1 The Atmosphere Gases Compared to the size of the Earth, the atmosphere is a thin shell. The part of the atmosphere we know best - the troposphere.

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Presentation on theme: "Atmosphere1 The Atmosphere Gases Compared to the size of the Earth, the atmosphere is a thin shell. The part of the atmosphere we know best - the troposphere."— Presentation transcript:

1 Atmosphere1 The Atmosphere Gases Compared to the size of the Earth, the atmosphere is a thin shell. The part of the atmosphere we know best - the troposphere - is an even thinner shell, only 12 kilometers (7.5 miles) thick. It is in the troposphere that all weather occurs; it is only here that life exists. The thin atmosphere lighted by the setting Sun.

2 Atmosphere2 Scientists View of Atmosphere

3 Atmosphere3 Variation of Temperature in the Atmosphere temperature

4 Atmosphere4 Air Composition at Sea Level Component Volume percent N O Ar0.934 CO Ne He CH Kr H N 2 O Xe O 3, SO 2, NO 2, NH 3, CO, I 2. trace Have you considered the atmosphere as sources of elements and compounds?

5 Atmosphere5 Water Vapor in the Atmosphere Explain these terms: Absolute humidity Partial pressure of water vapor Vapor pressure of water Relative humidity = Variation of water vapor pressure Partial pressure of water vapor Vapor pressure of water Discussed when we talk about gases, review please.

6 Atmosphere6 H 2 O (g) in Pacific during El Nino, Oct. 1997

7 Atmosphere7 Thomson-Joule Effect A gas cools during expansion. The amount of cooling is proportional to the pressure difference at the throttle, and increases substantially when the starting temperature of the gas is reduced. Carl von Linde produced liquid air in 1895 using the Thomson- Joule effect. Under 1 bar air liquefies at 80 K. Simple throttling will not suffice to reach this temperature. Linde introduced "countercurrent cooling".

8 Atmosphere8 Liquefaction of Gases Heat is always required to convert the liquid into its gas. Reducing pressure lowers the b.p., and cools the liquid. Liquid (high P )  Liquid (low P &T ) + Vapor Compressor Evaporator

9 Atmosphere9 Getting N 2 from Air Distillation of liquid air separate O 2 from N 2. Which has a higher b.p. O 2 or N 2 ?

10 Atmosphere10 Physical Properties of O 2, N 2 & Ar PropertyO 2. N 2. Ar Melting point (K) Boiling point (K) Critical temperature (K) Enthalpy of vaporization kJ mol Color of liquidbluecolorlesscolorless

11 Atmosphere11 Nitrogen Compounds Ammonia and related compounds NH 3, RNH 2, RR’NH, NH 4 +, (NH 2 ) 2 CO (urea), amino acids Nitrogen oxides and related compounds N 2 O, (anesthetic) NO, (maintain blood pressure, thins blood vessels) N 2 O 3, NO 2, (photochemical smog, brown)  N 2 O 4 (colorless) N 2 O 5 Acids HNO 3 HNO 2 How are some of these prepared?

12 Atmosphere12 Oxygen Production: Isolation from air (30 million tons) lab methods of preparation Uses manufacture of iron and steel manufacture and fabrication of metals manufacture of chemicals (oxidant) water treatment rocket fuel medicine uses petroleum refineing

13 Atmosphere13 Ozone Chemistry 3 O 2 (g)  2 O 3 (g)  H = 285 kJ O 2 (g) + h v  O (g) + O (g) O 3 (g) + h v  O 2 (g) + O (g) O 3 (g) + O  2 O 2 (g)  H = – 390 kJ Uses water treatment (substitute for Cl 2 ) oxidant (more powerful than O 2 ) waste water treatment

14 Atmosphere14 Ozone in the atmosphere Formation of ozone O 2 + h v  O + O O 2 + O  O 3 O 2 + O + M  O 3 + M* Absorption of UVB by ozone O 3 + h v  O + O 2 O 3 + O  2 O 2 Depletion of ozone by CFC Cl + O 3  ClO + O 2 O 3 + h v  O + O 2, ClO + O  Cl + O 2 O + O 3  O 2 + O 2. A major source of chlorine is Freons: CFCl 3 (Freon 11), CF 2 Cl 2 (Freon 12), C 2 F 3 Cl 3 (Freon 113), C 2 F 4 Cl 2 (Freon 114). Freons decompose in the troposphere. For example, CFCl 3  CFCl 2 + Cl CF 2 Cl 3  CF 2 Cl + Cl.

15 Atmosphere15 The Carbon Cycle See diagram in text and other sources

16 Atmosphere16 Carbon Dioxides in the Atmosphere Variation of CO 2 in the atmosphere

17 Atmosphere17 Hydrogen Productions C (coal) + H 2 O (g)  CO (g) + H 2 (g) (water gas) CO + H 2 O (g)  CO 2 (g) + H 2 (g) CH 4 (g) + H 2 O (g)  CO (g) + 3 H 2 (g) (fuel) Compounds HCl NH 3 (the Haber process) Metallic hydrides NaH, LiAlH 4, PdH x, CaH 2 Hydrogenation reactions CH 3 CH 3 CH 3 – C = C – CH 3 + H 2  CH 3 – C – C – CH 3 HH Find applications of N 2, O 2, & H 2

18 Atmosphere18 Self Study Guide Expect quantitative test questions in chapter 8 as in other chapters. Representative problems from Chapter 8 are: 30 – find enthalpy for NH 3 + NO = N 2 + H 2 O (balance, use  H f ; soln is incomplete) 36 – press of a gas containing 5e12 O 3 molecules 39 – 55 L gas at 145 atm and 26 o C, V = ___ at STP 41 – density of 79% He and 21% O 2 by volume at STP? 47 – determine heat of combustion 54 – stoichiometry problem 56 – stoichiometry and gas problem 59 – relative humidity (Chapt 8 problems) 61 – partial pressure problem There is no need to memorize sources and uses of the atmospheric gases.


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