Chapter 1: The Air We Breathe

1
Chapter 1 The Air We Breathe
Chem 100 Lecture 1 January 18, 2005
2
2004 Air Quality Data (EPA) for
Portland/Vancouver Metro Area
http//www.epa.gov/air/data/monaqi.html?stOROreg
on
3
Air Quality for the Country
http//www.epa.gov/airtrends/non.html
4
Primary components of air

• Nitrogen 78
• Oxygen 21
• Argon lt 1
• Inert (not very reactive) substance
• Carbon Dioxide lt 0.04
• Water Vapor
• Amount of water in air is
• 0 6 because it is so variable, we
  consider dry air.

5
What do we mean by ?

• by weight?
• by volume?

• Nitrogen 78
• Oxygen 21

For this mixture of 2 hypothetical compounds,
there appears to be 50 of by volume but only
10 of by weight.
0.1 g
10g
6
Some notes about volume

• Volume of gases depend on pressure and
  temperature
• The higher the pressure, the smaller the volume
  P V
• The higher the temperature the larger the
  volume T V
• All reported s refer to a specified pressure
  and
• temperature.
• Volume is reported in liters (L) the metric
  unit of volume
• 1 L 1.06 quarts

7
Volumes and particles

• It turns out that equal volumes of gases at the
  same temperature and pressure contain the same
  number of particles
• This means that volume particle
• So 78 of nitrogen means
• 78 L of nitrogen for every 100 L of air
• AND
• 78 particles of nitrogen for every 100 particles
  of air

8
Intro to the ppm unit

• Very small concentrations of pollutants can cause
  big problems.
• Ex The EPA regulation for sulfur oxides is
  0.000003
• Better units to use (so dont have to use all
  those zeroes?)
• PPM parts per million
• percents deal with 100 particles of air
• ppm deals with 1,000,000 particles of air

9
Converting between ppm and
1 1 particle per 100 particles 10
particles per 100 particles 100
particles per 10,000 particles 1000
particles per 100,000 particles 10,000
particles per 1,000,000 particles 1 10,000 ppm
1 million!
10
Conversion Problems to ppm
To convert from to ppm, move the decimal 4
places to the right. OR Unit factor method, with
the conversion factor 1 10,000 ppm
Example What is 0.007 in ppm? 0.007 70
ppm 0.007 x 10,000 ppm 70 ppm
1
11
Conversion Problems ppm to
To convert from ppm to , move the decimal 4
places to the left. OR Unit factor method,
with the conversion factor 1 10,000 ppm
Example What is 480 ppm?
480.0 0.048 480 ppm x 1
0.048 10,000 ppm
12
Scientific Notation

• 10 10 1 x 101
• 100 10 x 10 1 x 102
• 1000 10 x 10 x 10 1 x 103
• 0.1 1/10 1 x 10-1
• 0.01 1 / (10 x 10) 1 x 10-2
• This is useful for very large numbers
• In 1 L of air at 25oC and 1 atm pressure there
  are
• 2.5 x 1022 particles 250,000,000,000,000,000,
  000,000

13
More examples

• 1,000,000
• 0.03 ppm
• 0.000003

1 x 106
3 x 10-2 ppm
3 x 10-6
14
Regions of the Atmosphere

• No clear boundary b/w atmospheric regions.
• Troposphere is the region with most direct
  effects (air quality, weather)
• Other regions also affect usnote that the
  ozone layer is in stratosphere

15
Pressure vs. Altitude

• Pressure drops as altitude increases b/c gravity
  has less pull on the molecules (air density
  decreases).
• This is why there is less O2 at higher altitudes.

The of O2 and N2 remains the same at all
altitudes.
16
Air pollution
17
Health Effects of Some Pollutants

• Carbon monoxide
• Molecules of CO bind to the hemoglobin in red
  blood cells better than O2 so O2 cannot be
  delivered to the body.
• Ozone
• Decomposes quickly to form free radicals which
  can cause cellular damage (one of the purposes of
  antioxidants is to bind to free radicals)

Permissible limits are different Carbon
monoxide 9 ppm Ozone 0.12 ppm (more
hazardous than CO)
18
Classification Scheme for Matter

• Knowing the chemical make-up of air pollutants
  will helps us understand
• How they are produced
• 2) Why they are toxic
• Classification is the first step to understanding
  the chemical make-up.

19
Mixtures

• Mixtures are a physical combination of 2 or more
  substances that may be present in variable
  amounts.
• Example Air
• Pure air polluted air differ in composition.
  As composition varies, so do the properties.
• Other examples
• 1) Bowl of soup
• 2) Blood

20
Chemical Elements
Chemical elements are pure substances that cannot
be broken down into simpler substances by any
chemical means. Examples Oxygen and nitrogen,
the two most abundant compounds in air. Each
element is given a symbol Oxygen O
Hydrogen H Carbon C Iron
Fe
21
Periodic Table
Elements in the same column have similar
reactivities.
22
Compounds

• Compounds are pure substances made up of two or
  more elements in a fixed ratio (same composition)
• Examples
• 1) Water in one molecule of water, there are
• always 2 H atoms, 1 O atom
• Chemical formula H2O
• 2) Carbon dioxide in one molecule of carbon
  dioxide there are always 1 C atom, 2 O atoms
  Chemical formula CO2

Compounds can be broken down into their
component elements. Ex If an electric current
is applied to water, H2 and O2 gas will be
generated.
23
Classification exercise
v
v
v
v
24
Naming compounds

• Rules for compounds with 2 elements
• Name of the more metallic element comes 1st name
  of the less metallic element is modified to end
  in ide
• - Which of 2 elements is the more metallic
• element? The one furthest left on the
• periodic table.

25
Examples

• 1) Name of the compound containing
• oxygen (O) and magnesium (Mg)?

Magnesium oxide Formula MgO
2) Name of the compound containing hydrogen (H)
and chlorine (Cl)?
Hydrogen chloride Formula HCl
26
In actuality naming compounds a bit more
complicated

• Not all compounds have 1-to-1 ratios of elements
  like HCl and MgO
• Ex CaCl2 (calcium chloride)
• H2S (hydrogen sulfide)
• Goal for this course is for you to able to name a
  compound when shown its formula

27
Prefixes used in naming compounds
Prefixes help eliminate ambiguity about the
number of atoms of an element in a
compound. Example CO2 carbon dioxide
CO carbon monoxide
Note that most compounds in which a formula
contains only 1 atom of the element, the mono
prefix is omitted (carbon monoxide is an
exception and contains this prefix to avoid
confusion with carbon dioxide).
28
More Examples

• ZnO ?
• SO2 ?
• SO3 ?
• NO ?
• NO2 ?
• O3 ?

Zinc oxide
Sulfur dioxide
Sulfur trioxide
Nitrogen monoxide
Nitrogen dioxide
OZONE