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