Ozone Story Flashcards
Convert 339ppm into a percentage
399/1 000 000 = 3.99 x 10^-4
Multiply by 100 to get percentage = 0.04%
Or just divide by 10 000
How would you calculate the frequency of light given the wavelength?
c = w x f
speed (3 x 10^8) = wavelength x frequency
What four ways can matter react to electromagnetic radiation and what type of radiation causes this?
Translation (lowest energy)
Rotation (caused by microwave)
Vibration (caused by infrared)
Electron energy (highest energy - caused by UV and visible light)
Name 3 intermolecular forces
Induced dipole bond (van der Waals Forces)
Permanent dipoles
Hydrogen bonding
Explain induced dipole bonding
An induced dipole occurs if an unpolarised molecule is next to a dipole, which attracts/repels e- in the unpolarised molecule. Can be induced by a permanent. or induced dipole. Weakest type of intermolecular force. Increases with increasing Mr.
Why do branched alkanes have lower boiling points than straight chain alkanes?
Branching means molecules cannot pack as tightly together, weakening the Van Der Waals forces, requiring less energy to break so having a lower bp.
Explain permanent dipoles
When atoms in a molecule have different electronegativity, a dipole is formed, often creating a lattice structure
Explain hydrogen bonding
The strongest intermolecular force. Only forms between Hydrogen and Nitrogen, Oxygen and Fluorine, the most electronegative atoms. Resulting in a high melting and boiling point.
Define activation energy
The minimum energy required for a reaction to take place between colliding particles
What are three benefits of using a catalyst in industrial reactions?
Lowers energy cost
Higher atom economy
Increases sustainability (by lowering temp. and energy demand)
Define homogeneous catalysts
A catalyst in the same phase as the reactants and products
Why does the shape of the Maxwell-Boltzmann distribution not change even if you change conc. pressure or surface area?
Increasing conc., pressure or surface area of reactants means that successful collisions happen more frequently however the energy of individual particles do not change, so the graph does not change shape.
How does the addition of a catalyst affect the Maxwell-Boltzmann distribution?
The position of the activation energy shifts to the left so a greater proportion of particles have enough energy to react
Explain what primary, secondary and tertiary haloalkanes are
If the carbon bonded to the halogen has a single carbon chain, it is a primary haloalkane, and so on
How does rate of reaction change as you go down group 7 for haloalkanes? Why is this unexpected?
Rate of reaction increases as you go down the group, as the greater the Mr of the halogen the lower the bond enthalpy, despite electronegativity decreasing down the group.
Define nucleophile
An electron acceptor
Explain nucleophilic substitution
A nucleophile attacks a haloalkane: attacking the d+ carbon while electrons are transferred to the halogen
Define radical
A species with an unpaired electron
What is homolytic fission?
Each bonding atom receives an electron from the bonding pair, forming two radicals
What is heterolytic fission?
One bonding atom receives both electrons from the bonding pair, forming two ions
What are the three stages of the radical mechanism?
Initiation: Cl2 –> 2Cl.
Propagation: Cl. + CH4 –> .CH3 + HCl
.CH3 + Cl2 –> CH3Cl + Cl.
Termination: CH3 + CH3 –> C2H6
What are the environmental impacts of haloalkanes?
UV in stratosphere can cause CFCs (chlorofluorocarbons) to break down into radicals, breaking down ozone
Write out the radical mechanism for the breakdown of ozone
Overall: 2O3 --> 3O2 Initiation: CF3Cl --> .CF3 + .Cl Propagation: Cl. + O3 --> .ClO + O2 .ClO + O3 --> Cl. + 2O2 Chlorine radical is regenerated in second step so is catalytic in ozone breakdown
Why is ozone important for living organisms?
Ozone found mainly in the stratosphere absorbs UV light which can cause cancer and genetic damage
What is photochemical smog?
Reaction of nitrogen oxides with sunlight and ozone, damaging respiratory systems
How is the energy of a frequency of light calculated?
E = hv Energy = Planck's constant x frequency
Why are NO and NO2 unusual radicals?
They are both stable radicals and can be prepared and. collected like normal substances
