A Project of the American Chemical Society
PowerPoint slide presentation by Carl E. Heltzel,
Transylvania University
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter One
The Air We Breathe
The Composition of Our Air
It’s a mixture – a physical combination of two or
more substances present in variable amounts
1.2
Typical Composition of Inhaled and
Exhaled Air
Substance
What’s in
a Breath?
Nitrogen
Oxygen
Argon
Carbon
dioxide
Water
Inhaled
air (%)
78.0
21.0
0.9
0.04
Exhaled
air (%)
75.0
16.0
0.9
4.0
0.0
4.0
1.2
Concentration Terms
Parts per hundred (percent)
Atmosphere is 21% oxygen = 21 oxygen molecules
per 100 molecules of air
Parts per million (ppm)
Midday ozone levels reach about 0.4 ppm =
0.4 ozone molecules
1 x 106 molecules of air
Parts per billion (ppb)
Sulfur dioxide in the air should not exceed 30 ppb =
30 sulfur dioxide molecules
1 x 109 molecules of air
1.2
21% means 21 parts per hundred
means 210 parts per thousand
means 2,100 parts per ten thousand
means 21,000 parts per hundred thousand
The
difference
between
pph and
ppm is a
factor of
10,000
means 210,000 parts per million
Try Chapter 1 Figures Alive! for practice
1.2
EPA’s Air Quality Index
Air Quality Index Levels of Health
(AQI) Values
Concern
Colors
When the AQI
is in this range:
050
51–100
101–150
...air quality
conditions are:
Good
...as symbolized
by this color:
Green
Yellow
Orange
151–200
Moderate
Unhealthy for
sensitive groups
Unhealthy
201–300
301–500
Very unhealthy
Hazardous
Purple
Maroon
Red
1.3
Table 1.4 Air Quality Index values for Houston
Year
Good
(0–50)
Moderate
(51–100)
Unhealthy for
Sensitive Groups
(101–150)
Unhealthy
(>150)
1997
258
54
33
20
1998
253
70
23
19
1999
223
82
34
26
2000
166
147
37
16
2001
180
144
25
16
2002
196
136
24
9
2003
161
132
26
16
1.3
Air Pollutants: Risk Assessment
Toxicity – intrinsic health hazard of a substance
Exposure – the amount of the substance encountered
1.4
Characteristics of Risk Perception
Acceptable
Unacceptable
Exposure
voluntary
involuntary
Effect
immediate
delayed
Alternatives
none
many
Knowledge of consequence
known
unknown
Occupational encountered
yes
no
Image of hazard
common
dread
Severity of consequence
reversible
irreversible
Controllable
yes
no
1.4
The Regions of the Lower Atmosphere
Atmospheric pressure changes with altitude
1.5
Classifying Matter
All Matter
NO
Can it be separated by
a physical process?
Pure
Substances
NO
Elements
Can it be broken
down into
simpler ones by
chemical means?
YES
Mixtures
YES
Compounds
1.6
Classifying Matter
Classify each of these as an element, a compound, or a mixture:
carbon dioxide compound
nickel
element
cocaine
compound
water
compound
fluorine
element
table salt
compound
soap
mixture
sea water
mixture
1.6
The Periodic Table
Group
Period
A space filling model for a
water molecule, H2O
Oxygen atom
A molecule is a combination of a
fixed number of atoms held
together in a certain spatial
arrangement.
Two hydrogen atoms
The chemical formula
symbolically represents the type
and number of each element
present.
1.7
Many nonmetals occur as diatomic
(made up of two atoms) molecules
H2
N2
O2
Cl2
1.7
Naming Binary Compounds
1. Name the more metallic element first, followed by the name of
the less metallic element, modified with the suffix “ide”
KBr postassium bromide
BeO beryllium oxide
ZnS zinc sulfide
1.8
Naming Binary Compounds
2. Prefixes are used to designate the number of each type
of element:
number of atoms
prefix
1
mono
2
di
3
tri
4
tetra
5
penta
6
hexa
7
hepta
8
octa
9
nona
10
deca
1.8
Chemical reactions are characterized by the rearrangement
of atoms when reactants are transformed into products
C + O2
CO
reactants
product
This is an example of a
combustion reaction
But the number of atoms on each side of the arrow
must be equal (Law of Conservation of Mass)
2 C + O2
2 CO
(balanced)
2 carbon atoms
two carbon atoms
2 oxygen atoms
two oxygen atoms
1.9
2C
+
O2
2 CO2
+
1.9
Balancing equations:
-if an element is present in just one compound on each
side, balance it first
-balance anything that exists as a free element last
- balance polyatomic ions as a unit
- check when done – same number of atoms, and same
total charge on both sides
C3H8 + O2
C3H8 + 5 O2
3 C atoms
8 H atoms
10 O atoms
CO2 + H2O
3 CO2 + 4 H2O
3 C atoms
8 H atoms
10 O atoms
1.9
Direct Source of Sulfur Trioxide
Coal +
O2
SO2
(1-3% sulfur)
2 SO2
+
O2
2 SO3
Good News: Since 1985 we have seen a 25% reduction in SO2
emissions in the U.S.
1.11
Direct Source of Nitrogen Oxides
N2
+ O2 + high temp
NO is very reactive:
2 NO
+
O2
High temperatures
from auto engine or
2 NO
coal-fired power
(nitrogen oxide)
plant
Simplified version of
chemistry that occurs
2 NO2
1.11
Catalytic converters are used to catalyze the conversion of CO to CO2
The converters also reduce the amount of
Volatile Organic Compounds (VOCs) from
tailpipe exhaust
1.11
Formation of Tropospheric Ozone
NO2
sunlight
O + O2
NO + O
O3 is not directly emitted, it is
a secondary pollutantproduced from other pollutants
O3
Discuss the relationship
between hydrocarbon and
ozone concentrations in
the atmosphere
1.12
Ozone (O3)
If one breath of air contains 2 x 1022 molecules and atoms, and
the acceptable ozone level is 0.12 ppm, how many molecules
of O3 are in each breath?
2 x 1022 molecules and atoms in a breath of air x
0.12 O3 molecules
1 x 106 molecules
and atoms in air
= 2 x 1015 O3 molecules in a breath
How many oxygen atoms are in each breath?
2 x 1015 O3 molecules x 3 O atoms___
1 O3 molecules
= 6 x 1015 O atoms
1.12
Indoor Air Pollutants?
1.14