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The atmosphere is composed of the troposphere,
stratosphere, mesosphere and ionosphere, each layer
having distinctly different physical and chemical properties.
The troposphere is where wind, clouds and weather
occurs. The air pressure at the top of the troposphere is
1/10 atmosphere. The tropopause is a thin layer that separates
the troposhpere and the stratoshpere. The stratosphere
contains the thin ozone layer in its uppermost layer.
This layer is responsible for shielding us against the ultraviolet
rays from our Sun. Ozone (O3) is composed of
oxygen atoms that covalently bond in groups of 3 or
more and is made by natural sources of ionization (lightning
and mainly solar radiation) and more harmful man-made ionizing
sources (smog).
The mesosphere and ionosphere (thermoshpere) is where
many atoms are ionized (have gained or lost electrons so
they have a net electrical charge). The very thin ionosphere
is where the aurora borealis occurs, absorbs the most harmful
solar emissions and reflects long range radio communications.
The atmosphere in general is composed mainly of Nitrogen
(78%) and Oxygen (21%),
which are both diatomic gases (i.e. gaseous elements
that always travel in identical atom pairs, e.g. H2,
N2, O2, F2, Cl2,
Br2, I2). The Nobel (inert) gases
in the atmosphere are Ar Ne He Kr
and Xe.
ACID RAIN
Oxides of Nitrogen, Carbon and Sulfur all contribute to the
production of acid rain. The major sources of these oxides
include: combustion of hydrocarbons, bacterial action in soil,
forest fires, volcanic action and lightning. NO2 and NO products
both convert to nitric acid (HNO3) according to the
following reactions:
2NO + O2 => 2NO2
2NO2 + H2O => HNO2 + HNO3
Nitrogen and sulphur oxides are much lower in concentration
than CO2 (which is mainly responsible for making natural
rainwater slightly acidic) but NOx and SOx are much more
soluble than CO2 having the greater contribution to pH changes
in rainfall.
Investigate how smog
affects air quality using the SmogCity Lab
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| Gas
|
~%
of air |
nitrogen
oxygen
argon
CO2
neon
helium
CH4
krypton
N2O
hydrogen
xenon |
78
21
.9
.04
.002
.0005
.0002
.0001
.00005
.000005
.000009 |
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The General Gas Law
When an ideal gas is placed inside an airtight
container with an adjustable piston type lid it will behave
according to the General Gas Law (PV/T=P'V'/T').
If we don't allow the temperature (T) of the gas to change
the equation becomes Boyle's
Law (PV=P'V')
which basically states that the Pressure and Volume
of a gas sample are inversely proportional, i.e. when the
Volume decreases in the container the Pressure
increases. Volume can be measured in Liters, milliliters,
gallons, cubic inches, cubic centimeters (cc), etc. Pressure
can be measured in pounds per square inch (psi), pascals
(Newtons per square meter), atmospheres (atm), millimeters
mercury (mmHg), etc.
Here is a sample problem:
If a 6 Liter volume of Helium at a pressure of 3 atmospheres
is squished into 2 Liters, what is the new pressure inside
the container?
PV = P'V'
3atm x 6L = P' x 2L
(3 x 6) / 2 = P'
9atm = P'
So, when the volume was squeezed to 1/3 of
its original volume the pressure increased by 3 times! Since
pressure is caused by the density of atoms bouncing against
the walls of the container and we reduce the volume (increasing
the density) to increase the pressure it makes perfect sense.
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