Title: Lecture 33 Gases VIII The Atmosphere
1Lecture 33 - Gases VIII - The Atmosphere
2Smog
- Historically, Smoke Fog
- Urban smog a soup of oxidants, hydrocarbons
(HCs) and aerosols - NOx HCs light smog
3L.A. smog city
- 1. Lots of cars ( NOx HCs)
- 2. Lots of sunlight
- 3. Bowl shaped geography
- 4. Frequent temperature inversions
4Temperature inversions
T inversion (very stable)
z
usual
T
5Ground Level Ozone
- Ozone is cool (in the stratosphere)
- Ozone is not cool (in the air we breathe)
6Ground Level Ozone
- XO3 Symptom
- 5 x 10-8 headaches
- 1 x 10-7 eye irritation
- 2.7 x 10-7 coughing
- 2.9 x 10-7 chest pain
7September, 1979
- 10 consecutive days with
- XO3 gt 3.5 x 10-7
8The smog sequence
9Wheres the NO from?
- N2(g) O2(g) 2 NO(g)
- DGo 86.6 kJ/mol at 25oC
Kp exp (- DGo/RT)
6.6 x 10-16
10(pNO)2
Kp
pN2
pO2
(pNO)2 Kp
pN2
pO2
6.6 x 10-16 (0.78)(0.21)
in air
(pNO) 1.0 x 10-8 atm
in exhaust
11Formation of Ozone at Ground Level
- (2) HCs NO hn NO2 other stuff
12Radicals
- O atoms are radicals
- 1s22s22p4
- (2 short of an octet)
- thus, O is a strong oxidant
13Formation of Ozone
radical species (very reactive)
visible light
(4) O2 O O3 (5) NO ½ O2 NO2 (NO2 back!)
14Net Smog Reaction
- add reactions 3, 4 and 5
- 3/2 O2 hn O3
15Brownish Color of Smog
brownish
colorless
DHo lt 0
equilibrium shift upon increasing T
16Acid Rain
- 1. Produce SO2(g)
- S(in coal) O2(g) SO2(g)
- or
- NiS(s) 3/2 O2(g) NiO(s) SO2(g)
17Acid Rain
- 3. Form H2SO4
- SO3(g) H2O(l) H2SO4(aq)
a strong acid
18Whats the big deal about acid rain?
- 1. Lakes become acidic - fish dont like
- that.
- 2. Acid rain kills plant life.
- 3. Buildings dissolve.
19- CaCO3(s) H2SO4(aq)
- CaSO4(aq) H2O(l) CO2(g)
soluble, mechanically weak
20Other Interesting Gas Things...
- Air bags
- Refrigeration
- Supercritical Fluids
21Air Bags
D
- 2 NaN3(s) 2 Na(g) 3 N2(g)
- 10 Na(g) 2 KNO3(s)
- K2O(s) 5 Na2O(s) N2(g)
- K2O(s) Na2O(s) SiO2(s) a glass
22How do we cool gases to very low temperatures?
Use other gases! (Refrigeration)
23Pi
PfgtPi
Insulated Container
TfgtTi
24Compress a gas - it warms up
Expand a gas - it cools down
25Compressor
Expansion Valve
26Heat released
Compressor
Expansion Valve
27Heat released
Compressor
Expansion Valve
Heat Absorbed
28The best gases for refrigeration are CFCs!
- (Ozone eaters)
- Possible Solution The Sound Fridge
29The best gases for refrigeration are CFCs!
- (Ozone eaters)
- Possible Solution The Sound Fridge
Inert Gas
BIG speaker (160 dB)
30a standing (acoustic) wave
high pressure points (WARM!)
low pressure points (COLD!)
31Other neat gas stuff...
- If T is high enough, a gas can not be liquefied
at any pressure - happens if T gt Tc
critical temperature of gas
32G
L
TltltTc
TltTc
T³Tc