ATMOSPHERIC CHEMISTRY Flashcards
WHAT IS THE ATMOSPHERE?
the layer of air that extends about 100km above the surface of the earth
WHAT IS THE TROPOSHERE?
the bottom layer of the atmosphere. it contains about 90% of the air in the atmosphere
WHAT IS THE STRATOSPHERE?
the layer in the atmosphere that is found directly above the troposphere
WHAT IS THE COMPOSITION OF DRY UNPOLUTED AIR?
78% nitrogen
21% oxygen
1% other gases ( CO2 and Nobel gases)
WHAT IS OXYGEN ?
the most reactive gas in the atmosphere
WHAT ARE THE USES OF OXYGEN?
uses *in hospitals for people with breathing problems
*in the steel industry for removing impurities from , iron
WHAT IS NITROGEN
the most abundant gas in the atmosphere . it is inert due to the large amount of energy needed to break the triple bond
WHAT IS THE USES OF NITROGEN?
- to flush tanks of flammable liquids
- in food packaging to keep food fresh
- liquid nitrogen is used for fast freezing fruit
DESCRIBE HOW OXYGEN IS MANUFACTURED
LIQUEFACTION– used to turn air to liquid
- air is filtered to remove dust and then compressed
- CO2 and water vapour are removed
- air is then cooled to -170c by expanding it suddenly
- it is then further cooled to -200c
- the low temperature liquefies the air
FRACTIONAL DISTILATION–aloows nitrogen and oxygen in liquid air to be boiled off at different temperatures and to be separated from each other
- luquid air is passed into a fractionating column and allowed to slowly heat
- nitrogen boils off first at the top of the fractionating column due to its low billing point of -196c
- oxygen collects and boils off at the bottom of the fractionating column due to its higher boiling point of -183c
- this happens continuously due to air being constantly added and one end and product being continuously removed from the other end
STATE A CO PRODUCT OF THE MANUFACTURING OF OXYGEN
nitrogen
WHAT TWO SUBSTANCES ARE REMOVED BEFORE FRACTIONAL DISTILLMENT IN OXYGEN MANUFACTURING ?
water vapour and co2
IS THE MANUFACTURING OF OXYGEN CONTINOUS OR BATCH ? WHY ?
continuous as air is constantly being added at one end and products are constantly being removed at the other end continuously
DRAW A LABELED APPARATUS OF A FRACTIONATING COLUMMN MANUFACTURING OXYGEN
fractionating column , compressed liquid air , nitrogen at top , oxygen at bottom
WHY IS NITROGEN UNREACTIVE?
due to the large amount of energy that is needed to break the triple bond
WHAT IS LIQUEFACTION?
turning air to liquid
WHAT IS FRACTIONAL DISTILLATION?
allowing nitrogen and oxygen in liquid air to be boiled off at different temperatures and separated from each other
WHAT ARE THE TWO STEPS INVOLVED IN OXYGEN MANUFACTURING ?
liquefaction and fractional distillation
WHAT IS THE NITROGEN CYCLE?
it is a sequence of events which removes nitrogen from the air and then returns nitrogen to the air.
WHAT DOES THE NITROGEN CYCLE INDICATE?
it indicates the reason why nitrogen levels in the air remain mainly constant at around 78%
WHY CAN NITROGEN NOT BE USED BY PLANTS?
as nitrogen is unreactive
DESCRIBE THE NITROGEN CYCLE
NITROGEN FIXATION
–>unnatural-*haber process N2+3H3> 2NH3
- —>natural
- electrical storms
- lightening provides the heat needed for N2 to combust
- nitrogen combines with oxygen to create nitrogen monoxide
- nitrogen monoxide combines with oxygen to create nitrogen dioxide
- nitrogen dioxide combine with water to form nitrous acid and nitric acid
- nitric acid forms nitrates in the soil for plant roots to absorb to make plant protein
*legume plants
-legume plants in the soil have swellings on their root called nodules
-nodules contain rhizobium bacteria which convert nitrogen to nitrates
-plants absorbs the nitrates through their roots to make plant protein
ANIMALS
-animals eat the plants and convert the plant protein to animal protein
BACTERIA AND FUGI OF DECAY
-decay the dead plants and animal releasing nitrogen
- nitrogen is converted to ammonia by the bacteria and fungi
-also done in urea and sweat
NITRIFYING BACTERIA
-convert ammonia to nitrite and then nitrate
DENITRIFYING BACTERIA
-convert nitrates to nitrogen gas to be released into the atmosphere
DIAGRAM FOR NUTROGEN CYCLE
draw out check notes
WHAT IS NITROGEN FIXATION?
it is the conversion of nitrogen to compounds that can be absorbed by plants
HOW IS CARBON MONOXIDE FORMED?
when carbon is burned incompletely in limited oxygen
WHERE IS CARBON MONOXIDE FOUND?
in cigarette smoke or exhaust fumes in cars when the catalytic converter is not preforming efficiently
WHAT ARE THE PROPERTIES OF CARBON MONOXIDE?
- colourless gas with no smell
- neutral oxide( doesn’t react with acids or bases)
- poisonous( prevents oxygen being picked up by haemoglobin in the blood)
HOW IS CARBON DIOXIDE FORMED?
when carbon is completely burned in excess oxygen
WHAT ARE THE USES OF CO2?
used in fire extinguishers and to put fizz in drinks
WHAT IS FORMED FROM CARBON DIOXIDE
carbon dioxide is slightly soluble and when dissolved in water it forms carbonic acid > CO2+H2O–> H2CO3
PROPERTIES OF CARBON DIOXIDE?
- acidic oxide as it increases the hydrogen ion concentrayion in water giving it an acidic solution
- weak acid
WHAT OCCURS WHEN CARBON DIOXIDE IS DISSOLVED IN WATER
it forms carbonic acid
FORMULA FOR FERMENTATION
C6H12O6—–yeast—>2C2H5OH + 2CO2
WHEN DOES A CATALYTIC CONVERTER NOT PREFORM EFFICIENTLY ?
on short journeys
WHAT IS PRODUCED WHEN A CATALYTIC CONVERTER DOES NOT PREFORM EFFICIENTLY?
carbon monoxide
WHAT IS CARBONIC ACID?
it is a weak acid that diocciates further to produces hydrogen ions hydrogen carbonate ions and carbonate ions
WHAT DOES CARBONIC ACID FORM?
hydrogen ions , hydrogen carbonate ions and carbonate ions
WHAT ARE THE THREE SPECIES CARBONIC ACID CAN EXSIST AS?
hydrogen ions , hydrogen carbonate ions and carbonate ions
WHAT CAUSES ACIDIC RAIN?
carbon dioxide mixing with rainwater and producing carbonic acid which then causes acid rain by increasing the concentration of the hydrogen ions creating an acidic solution (ph 5-6)
WHAT IS THE CARBON CYCLE?
it is a process which removes co2 from the air , gets used by organism and the later returned to the air
WHAT DOES THE CARBON CYCLE INDICATE?
why the levels of co2 remain fairly constant at 0.03%
EXPLAIN THE CARBON CYCLE
1: plants removed co2 from the air to use in photosynthesis , they return the co2 to the air by respiration
2: animals obtain their co2 from consuming plants and then return it to the atmosphere by repiration
3: animals die and over millions of year form fossil fuels .the combustion of fossil fuel returns co2 to the air
4: if co2 mixes with water in rain water or sea water etc , if this water is used to form carbonate rocks eg limestone ,the roasting of this rock will release co2 back into the atmosphere
WHAT IS THE GREENHOUSE EFFECT?
it is when heat energy is trapped by gases in the atmosphere
WHY IS THE GREENHOUSE EFFECT ESSENTIAL?
to keep the earth heated
WHAT ARE GREENHOUSE GASES?
gases that adsorb heat in the atmosphere
WHAT IS THE GREENHOUSE FACTOR?
it compares the greenhouse effect of different gases ,relative to carbon dioxide
>water vapour = .1 >carbon dioxide = 1 >methane = 30 >dinitrogen oxide = 160 >CFC'S = 21,000-25,000
WHICH GAS CONTRIBUTES THE MOST TO THE GREENHOUSE EFFECT?why?
water vapour as it is there most abundant in the atmosphere
WHAT DOES THE CONCENTRATION OF WATER VAPOUR DEPEND ON?
the temperature , human activity has a very small effect on water vapour concentration
HOW HAVE HUMAN ACTIVITIES ENHANCES THE NATURAL GREENHOUSE EFFECT?
co2= burning of fossil fuel and respiration
meathane=natural gas leaks , rice paddy farms and waste dumps
dinitrogen oxide= car exhaust fumes
cfc’s= aerosol sprays , they are little amounts of cfcs in the air but they have a huge effect due to the larger greenhouse factor
WHAT ARE THE IMPLICATIONS OF THE EHANCED GREENHOUSE EFFECTS?
cause -global warming (the increase temp of the earth due to enhanced greenhouse effect)
- melting of ice caps
- climate change:drier summers and wetter winters
- rise in sea levels : causes flooding
HOW CAN GLOBAL WARMING BE REDUCES? 3 ways
- reduce the burning of fossil fuels and use more renewable energy sources
- ban cfcs and use cfc substitutes
- plant more trees
WHAT IS GLOBAL WARMING?
the increase of temperature of the earth due to enhanced greenhouse effect
WHAT DOES CLIMATE CHANGE CAUSE?
drier summers and wetter winters
WHAT IS AIR POLLUTION
a substance in the air to the extent that it poses a hazard to our health or the environment
WHY IS RAINWATER SLIGHTLY ACIDIC
as carbon dioxide dissolves in rain water to create a weak carbonic acid
WHAT IS THE PH OF RAINWATER?
5.6
WHAT ARE THE MAIN POLLUTANTS THAT CAUSE ACID RAIN?
sulphur dioxide and oxides of nitrogen
WHERE IS SULPHUR DIOXIDE PRODUCED NATURALLY?
in volcanoes and rotting vegetation
WHAT OCCURS WHEN SULPHUR DIOXOIDE DISSOLVES IN RAIN
so2+h20= h2so3
it creates sulphurous acid
NON NATURALLUY , HOW IS SULPHUR DIOXIDE PRODUCED?
by the burning of fossil fuels , mainly coal
S +O2 =SO2
HOW IS SULPHUR TRIOXIDE PRODUCED?
SO2 + 1\2 O2= SO3
HOW IS SULPHUR DIOXIDE PREVENTED BEING RELEASED INTO THE ATMOSHPERE?
CACO3 + SO2 = CASO3 + CO2
LIMESTONE SCRUBBERS ARE FITTED IN CHIMNEY STACKS OF COAL FIRED POWER STATIONS TO REMOVE SULPHUR DIOXIDE FROM THE GASES BEFORE THEY LEAVE THE POWER STATION
WHERE ARE OXIDES OF NITROGEN PRODUCED?
in electrical storms or nitrogen fixing bacteria
WHAT ARE THE EFFECTS OF ACID RAIN?
- kills the fish in lakes
- erodes limestone building and statues etc
- extracts minerals such as calcium and magnesium from the soil
WHAT IS THE IMPORTANCE OF THE OZONE
- it absorbs ultraviolet radiation preventing them from reaching the earths surface
- prevents sunburn and skin cancer
DESICRIBE THE FORMATION OF THE OZONE
o2 + o*= o3
- ozone is formed in the stratosphere
- ultraviolet radiation breaks oxygen molecules producing oxygen free radicle
- these oxygen free radicals combine with oxygen gas to produce the ozone
DESCRIBE THE DECOMPOSTION OF THE OZONE
03–> 02 + o*
the ozone absorbs ultraviolet light and photo- dissociation of ozone occurs breaking up the ozone into a oxygen molecule and a oxygen free radical
DESCRIBE THE REMOVAL OF THE OZONE
03+0*—-> 202
the oxygen free radical destroys the ozone by breaking it down to oxygen gas
WHY DOES THE OZONE NOT OCCUR IN THE TROPOSPHERE?
as there is a lack of ultraviolet radiation in the troposphere
WHAT CAN THE PRODUCTS OF THE OZONE DEPLETION AND REMOVAL BE USED FOR ?
can be used to form the ozone
WHY SHOULD THE OZONE IN THE STRATOSPHERE EXPECTED TO REMAIN CONSTANT?
as the ozone is being made constantly and destroyed constantly
WHEN AND WHERE WAS THE FIRST HOLE IN THE OZONE DISCOVERED?
in 1984 over the antarctic
WHAT IS THE STATE OF THE OZONE NOW AND WHY?
there is a general depletion of the ozone in many places over the world due mainly to chlorine atoms
WHAT IS A PHOTO CHEMICAL REACTION?
it is a chemical process that absorbs light energy to be used as its energy source eg : photosynthesis
WHAT ARE CFC’S
chlorofluorocarbons - compounds that contain chlorine , fluorine and carbon
GIVE TWO EXAMPLES OF CFC’S
dichlorofluromethane and dichlorodifluoromethane
STATE A FORMER MAJOR USE OF CFC’S
- fridges
- aerosols
- air conditioning
EXPLAIN HOW CFC’S GIVE RISE TO THE OZONE DEPLTETION
CCL3F —-> CCL2F + CL*
CL+ O3—>02+ CLO
CLO* + O—> CL + 02
chain reaction occurs as free chlorine oxide radicle reacts with more co3
PRPERTIES OF CFC’S
have long residency in troposphere ( up to 100 years) as they are stable and unnreactive
HOW DANGEROUS ARE CFC’S TO THE OZONE MOLECULES?
very dangerous , one CFC can destroy 100,000 ozone molecules
NAME A NON METAL OXIDE RESPONSABLE FOR DESTROYING THE OZONE IN THE STATOSHPERE
nitrogen monoxide from lightening NO + 03—> 02 + NO2
NAME A SUBSTANCE WHICH HELPS PREVENT DAMAGE TO THE OZONE LAYRE
methane , methane reacts with the chlorine atoms in the stratosphere to form hydrogen chloride gas
CH4 + CL*—–> CH3+HCL
NAME A REPLACEMENT FOR CFC’S
HCFC’S
WHAT ARE HCFC’S
hydrochlorofluorocarbons
compounds made up of hydrogen , chlorine , carbon and fluorine
WHY ARE HCFC’S LESS DANGEROUS THAN CFC’S
as they are broken down before they reach the stratosphere as they are more creative
GIVE ONE EXAPLME OF HCFC’S
chlorodifluoromethane
STATE 2 PROBLEMS ASSOCIATED WITH THE USE OF HCFC’S
- some still destroy they ozone as they contain chlorine
- contribute to global warming as its a greenhouse gas
NAME THE SUBSTITUE FOR CFC’S AND HCFC’S AND GIVE AN EXAMPLE
HCF’S hydrofluorocarbons
tetrafluoethane
