ENVIRONMENTAL CHEMISTRY
Muhammad Areeb Nafey uddin Siddiqui
Muhammad Aleem Ansari
Haadi Uddin Ahmed
Muhammad Hassaan Fawad
PERCENTAGE COMPOSITION OF AIR
Nitrogen-78%Oxygen-21%Noble Gases-0.97%Carbon dioxide-0.03%
VERIFYING COMPOSITION OF AIR
N2 + O2 + 2Cu heat 2CuO + N2
•where nitrogen remains unreacted.
VERIFYING COMPOSITION OF AIR: PROCEDURE
100 cm3 of dry air (air is dried by passing over anhydrous calcium chloride) filled in a graduated gas syringe
This air is passed back-and-forth over heated copper using two syringes, attached on each side of a hard glass (silica) tube (containing copper)
On culmination of the experiment, 79 cm3 of dry gas remains, indicating that 21 cm3 has been used by copper
On analysis, the remaining gas is found to be mainly nitrogen and pink copper metal turns to black copper (II) oxide
LIQUEFACTION OF AIR
Air is mainly comprised to two diatomic gases, namely nitrogen, N2, and oxygen O2
By principle, the liquefaction point of air should lie between those of pure N2 (77K) and pure O2 (90.6K)
The liquefaction process begins at 81.6K (9K below the liquefaction point of O2) and completes at 79K (2K above the liquefaction point of N2), at one atmospheric pressure
Industrially, however, 200 atm. is used, so aforementioned conditions do not necessarily apply
LIQUEFACTION OF AIR
LIQUEFACTION OF AIR—PROCESS
Repeated compression and expansion of gases until temperature drops to 73K
Air is compressed at 200 atmospheres
Water removed in a drying tower, containing silica gel
CO2 removed by bubbling through alkali
2NaOH + CO2 Na2CO3 + H2O
Dust removed
FRACTIONAL DISTILLATION OF LIQUID AIR
Pale blue liquid air passed in a fractionating column
Nitrogen starts to boil off first, at 77K
Argon boils off, at 87K
Oxygen boils off, at 90K
heat
87K
then
BOILING POINTS OF COMPONENTS OF AIR
Gas Boiling Point/K
Xenon 165
Krypton 121
Oxygen 90
Argon 87
Nitrogen 77
Neon 27
Helium 4
CARBON CYCLE—DIAGRAMMATIC
CARBON CYCLE
Earth’s crust contains carbon compounds (carbonates, fuels)
Atmosphere contains carbon in form of carbon dioxide, mainly released by respiration:C6H12O6 + 6O2 6CO2 + 6H2O (ΔH = -ve)
Also released when fuels combust:C + O2 CO2
CO2 used by plants to manufacture sugars, in photosynthesis:6CO2 + 6H2O C6H12O6 + 6O2 (ΔH = +ve)
Decomposition and fossilization return carbon compounds of living things to soil
PRIMARY POLLUTANTS OF AIR
Carbon monoxide Methane Nitrogen oxides Ozone Sulfur dioxide Unburnt hydrocarbons
CARBON MONOXIDE
Naturally produced by photochemical reactions in the troposphere (5×1012 kg/year), during breakdown of haemoglobin and in fires
Also produced due to incomplete combustion of hydrocarbons
Greenhouse gas Toxic gas, which is the main source of air
poisoning in most countries headache, nausea, vomiting, dizziness, fatigue disorientation, visual disturbance, syncope and
seizures
METHANE Produced naturally in rice paddies, decomposition
of biological matter, digestion, coalmines, sea beds (methane hydrates)
Main constituent of natural gas If CH4 > O2 in blood, displacement can occur (but
rarely), leading to slight emotional, psychological distress, and fatigue
Non-carcinogenic and generally not harmful to health
Contributes in ozone depletion Displaces air, i.e., acts as an asphyxiant:
CH4 + 2O2 CO2 + 2H2O
2CH4 + 3O2 2CO + 4H2O
CH4 + O2 C + 2H2O
NITROGEN OXIDES
Collectively known as NOx
Naturally produced during lightning bolts:
Also produced during combustion of fuels in automobiles (especially high-speed vehicles) and in electric power plants
Leads to increased smog, acid rain and water quality deterioration
Significant as an irritant of mucus membranes
OZONE
Found naturally in stratosphere & troposphere
Formed by photochemical reactions between volatile organic compounds and nitrogen oxides
Associated with increased mortality, especially in warm season
Affect plant mechanisms Affects health by:
decrements in lung function (like aggravating astma)
chest-related problems (coughing, tightness, burning)
decreasing phagocytic activity of alveolar macrophages
SULFUR DIOXIDE
73% of SO2 is released through fossil fuel combustion
20% of SO2 is released through other industrial processes (like smelting of ores)
Volcanic eruptions lead to increased emissions Leads to respiratory problems, like asthma Reacts with water vapour to form sulphurous
acid:SO2 (g) + H2O (g) H2SO3 (l)
This causes acid rain, that result in decomposition of important stonework & poisoning
UNBURNT HYDROCARBONS
Formed by low-temperature combustion of fossil fuels, and from fuel ‘avoiding’ the flame zones in combustion engines
Evaporation of petroleum also leads increased emissions
Hydrocarbons like benzene are carcinogenic and prevent normal cell metamorphosis
React with UV light and combine with other pollutants, especially NOx to form photochemical smog
GREENHOUSE EFFECT
EFFECTS OF GREENHOUSE GASES
CH4 and CO2 are the main greenhouse gases.
They maintain warmth on the earth that makes life possible on the plant.
Excess release of these gases causes them to be trapped in the atmosphere, thus they help the atmosphere retain more heat.
This leads to a phenomena called ‘global warming’, consequently leading to climate change.
Will lead to melting of ice caps and widespread flooding.
Desertification and loss of biodiversity may occur.
THE OZONE LAYER
30,000 metres above the mean altitude of the earth; lies in the stratosphere
Very warm, as absorbs UV light Stops clouds & water vapour from escaping Ozone depletion occurs due to CFCs (very
stable):Cl + O3 ClO + O2 ClO + O Cl + O2
O3+ O2 2O2 (overall) This is an autocatalysed reaction (chlorine) Ozone hole aver Antarctica Increased UV rays reach earth—skin cancers
REMEDIES FOR AIR POLLUTION
Flue gas desulphurisation stops SO2 emissions:
SO2 + CaCO3 → CaSO3 + CO2
Use of catalytic converters to render CO and NOx harmless:
2NO + 2CO → 2CO2 + N2
2NO2 + 4CO → 4CO2 + N2
Using low-temperature combustion engines with catalytic converters reduces NOx and unburnt hydrocarbons
Alternatives to CFCs be introduced Strict implementation of Montreal and Kyoto
Protocols be ensured
BIBLIOGRAPHY Chemistry—A Course for O-Level by
Christopher N. Prescott http://hyperphysics.phy-astr.gsu.edu/hbase/t
hermo/liqair.html GCSE Biology by D.G. Mackean http://en.wikipedia.org/wiki/Carbon_monoxid
e http://www.ccohs.ca/oshanswers/chemicals/c
hem_profiles/methane.html http://en.wikipedia.org/wiki/Methane http://chemwiki.ucdavis.edu/Physical_Chemis
try/Acids_and_Bases/Case_Studies/Acid_Rain/Sources_of_Nitrogen_Oxides
http://www.epa.gov/iaq/no2.html http://www.a2gov.org/government/publicservi
ces/systems_planning/Environment/soe07/cleanair/Pages/nox.aspx
http://www.epa.gov/apti/ozonehealth/population.html
http://www.epa.gov/region07/air/quality/o3health.htm
BIBLIOGRAPHY http://www.epa.gov/airquality/sulfurdioxide/ http://
www.epa.gov/airquality/sulfurdioxide/health.html
http://prezi.com/sp-kbyuw0v4v/methane-and-unburnt-hydrocarbons-consequences-and-resolutions/
http://en.wikipedia.org/wiki/Unburned_hydrocarbon
http://papers.sae.org/2009-01-2729/ http://
www.edfenergy.com/energyfuture/images/schematic/greenhouse-effect.jpg
Environmental Management—A Core Text for O Level and IGCSE by John Pallister
http://www.xtremepapers.com/revision/gcse/chemistry/air_and_water.php
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