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CHEMISTRY
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1 CHEMISTRY OF THE AIR
GREENHOUSE GASES
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Water vapour
Carbon dioxide
Methane

ABSORPTION OF INFRARED RADIATION
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Molecules of H2O, CO2 and CH4
Absorbed by C=O, O-H and C-H bonds
Molecule vibrates

VIBRATING MOLECULES
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Vibrate, rotate, stretch
Emit energy in form of radiation
Radiation absorbed by greenhouse gas molecules

DETERMINANTS OF THE GREENHOUSE EFFECT OF A GAS
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Atmospheric concentration in atmosphere
Ability to absorb IR radiation

ABSORPTION-EMISSION PROCESS
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Keeps heat close to Earth’s surface

GLOBAL WARMING
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Climate change
Caused by increase in greenhouse gases (burning coal, oil etc
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)
Hydrogen fuel cells for cars

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)
EU targets
Cleaner cars (less emissions of CO2)

CARBON CAPTURE AND STORAGE (CCS)
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Sequestration
Captures CO2 from power stations and stores it away safely

STORAGE IN OCEANS (CCS)
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Liquid carbon dioxide injected deep in the oceans

STORAGE UNDERGROUND (CSS)
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Store CO2 gas in underground porous rock (acts as a sponge)
Keep it from leaking away

STORAGE AS CARBONATES
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Storing carbon in stable minerals
Reaction between CO2 and metal oxides
Producing stable carbonates
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CaO (s) + CO2 (g)  CaCO3 (s)
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limestone rock (CaCO3)

Ozone
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O3
Continuously being formed and broken down
Broken down in stratosphere by UV radiation

CHEMICAL EQUILIBRIUM
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O2 + O ↔ O3

CYCLE
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UV radiation breaks O2 molecules into two oxygen atoms
O atoms react with O2 molecules
Process generates heat
O3 absorbs UV and converted back to O2 and O

BALANCE OF OZONE IN OZONE LAYER
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Ozone is being formed at the same rate as it is being broken down
Stable balance

BENEFITS OF THE ABSORPTION OF UV BY OZONE
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Process protects living organisms from harmful effects of UV
Ozone layer filters out short wavelengths
Ozone converts UV into heat

CFCs
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Non-toxic
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Formation of low-level ozone (troposphere)
Converted into nitric acid (acid rain)
Respiratory irritants

UNBURNT HYDROCARBONS
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Human carcinogens
Form low-level ozone with nitrogen dioxide

LOW-LEVEL OZONE
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Serious pollutant
Breathing difficulties
Increasing susceptibility to infections
Smog

CATALYTIC CONVERTER
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Fitted in cars
Decreases CO and NO emissions
Toxic  non-toxic and less harmful gases
Made from platinum, rhodium and palladium (catalytic surface)
Honeycomb arrangement – large surface area

OXIDATION CATALYSTS
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Decrease emissions of CO, nitrogen oxides and unburnt hydrocarbons
2CO (g) + O2 (g)  2CO2 (g)
C12H26 (l) + 181⁄2O2 (g)  12CO2 (g) + 13H2O (l)

THREE-WAY CATALYST
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2NO (g) + 2CO (g)  N2 (g) + 2CO2 (g)

HOW THE CATALYST FUNCTIONS
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Adsorption
Chemical reaction
Desorption

ADSORPTION
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CO and NO gas molecules diffuse over catalytic surface of metal
Molecules hold on to metal surface by adsorption
Temporary bonds form between catalytic surface and gas molecules

CHEMICAL REACTION
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Bonds hold gas molecules in correct position on surface
Chemical reaction
Bonding to catalyst surface is weak enough for adsorption and desorption to take place
Bonding is strong enough to weaken bonds and allow reaction to take place

DESORPTION

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Blowing agents
In manufacturing foam

CO2 AS A SOLVENT
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CO2 converted into supercritical fluid (altering TP)
scCO2
Used to dissolve reactants

CO2 FOR DECAFFEINATED COFFEE
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scCO2 for decaffeination
Flavouring remains
No problem with toxicity

CO2 FOR BEER
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scCO2 to extract flavour of beer from hops

CO2 FOR DRY CLEANING
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scCO2 as solvent to dissolve grease
Rather than chlorinated hydrocarbons

CO2 FOR TOXIC WASTE TREATMENT
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scCO2 dissolves and removes toxic materials from waste

SUSTAINABILITY
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Fossil fuels replaced by biodiesel, alcohol and fuel cells
Increased recycling of plastics, glass and metals

SIDE-EFFECTS
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Production of biodiesel uses grain crops
Land needed for food is used
Poorer countries are affected

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This work is shared under a Creative Commons Attribution-NonCommercial-NoDerivatives license

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