Atmospheric Chemistry Flashcards
what is the atmosphere?
a layer of gases
atmospheric composition: nitrogen
78%
atmospheric composition: oxygen
21%
how does oxygen exist
as oxygen gas O2
and ozone O3
manufacture of oxygen 2
extracted from the atmosphere by;
- liquifying the air
- fractionally distilling the air
manufacture of oxygen
first step
air is filtered to remove dust particles
manufacture of oxygen
how is carbon dioxide removed?
air is passed through sodium hydroxide to remove CO2
manufacture of oxygen
how is water removed?
water vapour condenses out during compression and in drying towers using silica gel
manufacture of oxygen
what occurs during compression
the air heats up
manufacture of oxygen
how to cool air
the air is passed through a heat exchanger where it is cooled by cold nitrogen in a fractioning column
manufacture of oxygen
in fractioning tower
liquified air is distilled, oxygen collects at he bottom and nitrogen at the top
manufacture of oxygen
why is oxygen further purified
purified to remove inert gases such as neon and krypton
4 uses of oxygen
steelmaking
welding
medicine
recreational
steelmaking - use of oxygen
to remove carbon, silicon and phosphorous from cast iron as there oxides
welding - use of oxygen
when ethyne is burned in oxygen temperatures of about 3000ºC are reached
how is nitrogen found?
as N2
is nitrogen gas reactive or unreactive?
chemically unreactive due to the high bond energy of the triple bond between its atoms
why is nitrogen important
as it is a constituent of protein that is essential for muscle cells and blood cells
Natural Fixation of Nitrogen
any process that produces useful compounds from atmospheric nitrogen
3 natural fixation of nitrogen methods
lightning
bacteria
decomposition
how does lightning naturally fixate nitrogen?
at very high temperatures nitrogen and oxygen combine to form nitrogen monoxide, then combines with atmospheric oxygen to form nitrogen dioxide - dissolves in rain water to give nitrous and nitric acids, HNO2 and HNO3. fall on earth and deposited in soil, make plant protein
how does bacteria naturally fixate nitrogen?
certain species are capable of fixing atmospheric nitrogen into nitrates that plants can absorb to make plant proteins.
some are free in soil - Azotobacter, some in plants eg. clover and sweet pea - Rhizobium
how does decomposition naturally fixate nitrogen?
most of the nitrates in soil come from dead and decaying plants and animals
an example of an artificial fertiliser
ammonium nitrate
4 uses of nitrogen
freezing food
packaging of food
reduce the flammability of chemicals
manufacture of ammonia and nitric acid
how does nitrogen help with freezing food?
liquid nitrogen is used to fast freeze foods which is less damaging to food than normal freezing
how does nitrogen help with packaging food?
crisps are packed in nitrogen as it prevents oxidation of the oils
how does nitrogen reduce the flammability of chemicals?
nitrogen is used to reduce the oxygen content in storage tanks, thus reducing the flammability of certain chemicals
it is also used to flush out dangerous vapours in tanks
manufacture of ammonia
nitrogen is used as feedstock in the manufacture of ammonia
equation for how lightning naturally fixates nitrogen
N2 + O2 -> 2NO
heat change of how lightning naturally fixates nitrogen
endothermic
shape of CO2
linear
Combustion of carbon dioxide eqn.
C + O2 -> CO2
carbon dioxide as an acid in water
CO2 + H2O -> H2CO3
H2CO3
carbonic acid (weak)