Ozone

Troposphere - bottom layer    Stratosphere - ozone

Gas percentages in air

• 78% Nitrogen
• 21% oxygen 
• 399ppm CO₂
• 0.93% Argon

Converting between % and ppm

• % - ppm multiple by 10000
• ppm - % divide by 10000

Solar energy

• Radiowaves stopped by atomosphere
• x rays and gamma rays lost in magnetosphere

UV light

• high energy UV radiation absorbed by ozone 
• breaks DNA bonds (photodissociation) causing mutation/skin cancer

Ozone

• highly reaction
• tropospheric ozone formed from exhaust gases and unburnt hydrocarbons

Energy equations

• wave speed = frequency x wavelength
• energy = plank constant x frequency

Molecule behaviour

• visible light/UV promotoes electrons
• infrared causes vibration
• Microwaves causes rotation
• Temperature above Kelvin causes translation

Calculating frequency from bond enthalpy

• Divide by Avogadro's constant
• Convert energy to joules
• use E=hv to work out frequency

Heterolytic bond fission - forms ions

Homolytic bond fission - forms radicals 

Radicals - species with an upaired electron

Chain reaction

• Initiation
• propagation
• Termination

Steady state reaction - rate of formation = rate of destruction 

Forming ozone

• O₂ + high energy UV --> 2O
• O₂ + O --> O₃
• O + O --> O₂

Destruction of ozone

• O + O₃ --> 2O₂
• O₃ + high energy UV --> O₂ O

• temperature
• surface area
• catalyst
• radiation intensity
• pressure

Activation energy - minimum amount of energy required to break bonds

Maxwell - Boltzmann distribution curve

• area under graph = number of particles
• increase in temperature - graph moves to right and is lower down
• catalyst changes Ea line

General rule- increase by 10 derees, rate is doubled

Polarity

• when one atom higher charge denisty then the other 
• due to a difference in electronegative

Electronegativity

• measure of ability of an atom in a molecule to attract electrons in a chemical bond to itself

Intermolecule forces

• Instantaneous dipole - induced dipole
• permanent dipole - induced dipole
• permanent dipole - permanent dipole

Boiling points

• increased carbon chain = stronger bonds due to larger number of electrons
• branching decreases strength of bonds reducing contact points

Hydrogen bonding

• type of permanent dipole - permanent dipole 
• molecule 1: H atom attached to highly electronegative atom
• molecule 2: highly electronegative atom with at least one lone pair of electron

Chlorofluorocarbons

• low toxicity
• non-flammable 
• high stability

Hydrofluorocarbons (HFC) - fluorine radicals aren't formed in stratosphere

Hydrochlorofluorocarbons (HCFCs) - C-H bond broken in low troposphere 

Haloalkanes

• C-F bonds can't undergo photodissociation 
• C-Br / C-I broken lower in troposphere 

Chlorine

• CH₃Cl undergoes photodissociation to create Cl radical
• homogeneous catalysts 
• X + O₃ --> O₂ + XO
• XO + O --> O₂ + X