Download Atmosphere Gases and Hydrogen

The Atmosphere Gases
The thin atmosphere
lighted by the setting
Sun.
Atmosphere
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.
1
Scientists View of Atmosphere
Atmosphere
2
Variation of
Temperature
in the
Atmosphere
temperature
Atmosphere
3
Air Composition at Sea Level
Component
Volume percent
N2
O2
Ar
Have you
CO2
considered the
Ne
atmosphere as
He
sources of
CH4
elements and
Kr
compounds?
H2
N2O
Xe
O3, SO2, NO2, NH3, CO, I2
78.084
20.946
0.934
0.037
0.001818
0.000524
0.0002
0.000114
0.00005
0.00005
0.000009
.
trace
Atmosphere
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Water Vapor in the Atmosphere
Explain these terms:
Absolute humidity
Partial pressure of water vapor
Vapor pressure of water
Partial pressure of water vapor
Relative humidity =
Vapor pressure of water
Variation of water vapor pressure
Discussed when we talk about gases,
review please.
Atmosphere
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H2O (g) in Pacific during El Nino, Oct. 1997
Atmosphere
6
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 ThomsonJoule effect.
Under 1 bar air liquefies at 80 K. Simple
throttling will not suffice to reach this
temperature. Linde introduced
Atmosphere
"countercurrent cooling".
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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
Atmosphere
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Getting N2 from Air
Distillation of liquid air separate O2 from N2.
Which has a higher b.p. O2 or N2?
Atmosphere
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Physical Properties of O2, N2 & Ar
Property
Melting point (K)
Boiling point (K)
Critical temperature (K)
Enthalpy of vaporization kJ mol-1
Color of liquid
Atmosphere
O2.
N2.
54.8 63.1
90.2 77.4
154.6 126.2
3.41 2.79
Ar
83.8
87.3
150.8
6.5
blue colorless colorless
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Nitrogen Compounds
Ammonia and related compounds
NH3, RNH2, RR’NH, NH4+, (NH2)2CO (urea), amino acids
Nitrogen oxides and related compounds
N2O, (anesthetic)
NO, (maintain blood pressure, thins blood vessels)
N2O3,
NO2, (photochemical smog, brown)  N2O4 (colorless)
N2O5
Acids
HNO3
HNO2
How are some of these prepared?
Atmosphere
11
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
Atmosphere
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Ozone
Chemistry
3 O2 (g)  2 O3 (g)
H = 285 kJ
O2 (g) + h v  O (g) + O (g)
O3 (g) + h v  O2 (g) + O (g)
O3 (g) + O  2 O2 (g) H = – 390 kJ
Uses
water treatment (substitute for Cl2)
oxidant (more powerful than O2)
waste water treatment
Atmosphere
13
Ozone in the atmosphere
A major source of chlorine is Freons: CFCl3 (Freon 11), CF2Cl2 (Freon
12), C2F3Cl3 (Freon 113), C2F4Cl2 (Freon 114). Freons decompose in
the troposphere. For example,
CFCl3  CFCl2 + Cl
CF2Cl3  CF2Cl + Cl.
Formation of ozone
O2 + h v  O + O
O2 + O  O3
O2 + O + M  O3 + M*
Depletion of ozone by CFC
Cl + O3  ClO + O2
O3 + h v  O + O 2,
ClO + O  Cl + O2
O + O 3  O2 + O 2.
Absorption of UVB by ozone
O3 + h v  O + O 2
O3 + O  2 O 2
Atmosphere
14
The Carbon Cycle
Atmosphere
See diagram in text and other sources
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Carbon Dioxides in the Atmosphere
Variation of CO2 in the atmosphere
Atmosphere
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Hydrogen
Productions
C (coal) + H2O (g)  CO (g) + H2 (g) (water gas)
CO + H2O (g)  CO2 (g) + H2 (g)
CH4 (g) + H2O (g)  CO (g) + 3 H2 (g) (fuel)
Compounds
HCl
NH3 (the Haber process)
Metallic hydrides NaH, LiAlH4, PdHx, CaH2
Hydrogenation reactions
CH3
CH3
CH3 – C = C – CH3 + H2  CH3 – C – C – CH3
H H
Find applications of N2, O2, & H2
Atmosphere
17
Self Study Guide
Expect quantitative test questions in chapter 8 as in other chapters.
Representative problems from Chapter 8 are:
30 – find enthalpy for NH3 + NO = N2 + H2O (balance, use Hf; soln is incomplete)
36 – press of a gas containing 5e12 O3 molecules
39 – 55 L gas at 145 atm and 26o C, V = ___ at STP
41 – density of 79% He and 21% O2 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.
Atmosphere
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