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What happened to change the
opinion of CFC’s?
However, CFCs damage ozone in the
ozone layer when they escape into
the atmosphere
...
When scientists
discovered that CFCs damage the
ozone layer, they suggested that CFCs
should be banned
...

http://www
...
co
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For
example:





They are chemically inert (unreactive)
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These properties made CFCs very
useful in the past
...
They were also used in
aerosol cans as propellants (the gases
that push the product out through the
nozzle)
...
bbc
...
uk/schools/gcsebitesize/s
cience/triple_ocr_gateway/chemistry_out_th
ere/depletion_of_ozone/revision/2/
Due to their chemical properties, CFCs
became useful as coolants and propellants
...

The other main use for CFCs has been as a
propellant for aerosol cans
...
Some of the
common uses were hairspray, spray paint,
and cooking spray
...
com/academy/lesson/cfcsdefinition-properties-uses
...
In
addition to carbon atoms, CFC
molecules contain chlorine and
fluorine atoms
...
bbc
...
uk/schools/gcs
ebitesize/science/triple_ocr_gate
way/chemistry_out_there/depleti
on_of_ozone/revision/2/
A common subclass is the hydro
chlorofluorocarbons (HCFCs),
which contain hydrogen, as well
...

http://www
...
com/cf
c
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They are like CFC
molecules, except hydrogen atoms
have replaced some chlorine atoms
Advantages and Disadvantages of HCFCs
Advantages

Disadvantages

Replacement of the chlorine
atom(s) with hydrogen atoms means
Still contains chlorine that can
that less chlorine atoms are released
attack the ozone layer
to the stratosphere --> ODP
Can contribute to global warming
decreased
(it’s a greenhouse gas)
Extra hydrogen (H) dissipates
More expensive to produce than
almost all the chlorine in the
CFCs
troposphere before the chlorine can
reach the ozone layer (the extra
hydrogen makes them have a lower
stability than CFCs) --> lower ODP
than CFCs (only 2% - 10% of CFCs’)
Lower atmospheric lifetimes (2 - 25
years) than CFCs (100 years or more)
Low toxicity; no or low
flammability; do not produce smog

http://www
...
ca/projects/2008/laic8c2/pres
ent_subs
...
Take a
look at these equations:
1
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3
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CFC molecules reach the
stratosphere
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For example:
CCl3F → •CCl2F + •Cl
The chlorine atoms are called
chlorine radicals
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2
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http://www
...
co
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The Parties to the
Montreal Protocol have amended the
Protocol to enable, among other
things, the control of new chemicals
and the creation of a financial
mechanism to enable developing
countries to comply
...
unep
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CFCs are broken down slowly by ultraviolet
radiation, so they are only slowly removed
from the stratosphere
...
When a CFC
molecule absorbs ultraviolet radiation, a
carbon-chlorine bond breaks
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