Ozone Story Flashcards
What are the 3 types of intermolecular bonds
1) instantaneous dipole- induced dipole
2) permanent dipole-permanent dipole
3) hydrogen bonds
How do instantaneous dipole- inducer dipole bonds work?
1) electrons are always moving causing charge density to change making instantaneous dipoles
2) this can induce a dipole be attracted towards it creating an instantaneous- induced bond
(The bonds get broken and remade because electrons keep moving)
How does a molecules shape affect its intermolecular bonds?
More places for id-id bonds to form if it had a longer chain
Branch chains can’t get as close
Why does a molecules size and mass effect boiling point?
The bigger the molecule the larger electron cloud which means it forms stronger id-id bonds
What do bonds need to be in order to have a pd-pd bond?
Polar
When can hydrogen bonding happen and why?
When a hydrogen is attached to a fluorine, nitrogen, or oxygen.
Very electronegative with hydrogen - high charge density on the H
What does electronegative mean?
Tendency to attract electrons and form negative ions
Two ways hydrogen bonds affect how a substance behaves
1) hydrogen bonding is a very strong intermolecular bond giving the substance a high melting point as it’s hard to over come
2) soluble in water - can form bonds with the water making it soluble
How can an experiment show differences in bond strengths
Energy is absorbed to break bonds when a liquid evaporates
so you can measure the temperature change in order to see how easily a liquid evaporates
and what type of intermolecular bonds it’s likely to form
What is the collision theory
Particles must collide with:
- correct orientation
- enough kinetic energy to react (activation energy)
How would increased temp change the Boltzmann distribution graph?
- moves it to the right
- reduces hump
- more molecules with enough activation energy to react
How do catalysts affect reaction rate?
- lowers activation enthalpy by providing an alternative pathway (a different way for bonds to be broken and remade)
- so more particles have enough energy to react
How does pressure and concentration affect reaction rate?
- particles are closer together on average
- collide more often so have more chances to react
How does temperature affect reaction rate?
- particles have more energy so more likely to react when they collide
- move faster - collide more frequently
How can you use experiments to find out rate of reaction?
Measure loss of reactant of formation of product at regular intervals
What is a catalyst
A catalyst increases rate of reaction by providing and alternative reaction pathway with lower activation enthalpy
Catalyst is chemically unchanged at the end and reformed
Two types of catalyst
Homogeneous - same state heterogeneous - different state
How do homogeneous catalysts work?
- by forming intermediated
- the activation enthalpy needed to make intermediates and form the product is lower than reactants straight to products
- catalyst reformed again
How many jumps does a homogeneous catalyst reaction have?
2 from making intermediates
Do boiling points of haloalkanes increase or decrease down the group?
Increase
Stronger id-id bonds because molecules are bigger due to more electron levels
Why are carbon-halogen bonds polar
How does this affect the molecule?
High difference in electronegativity
Carbon becomes electron deficient so it can be attacked by a nucleophile
What is a nucleophile?
Give an example
An electron pair donor
OH-
NH3
What is nucleophilic substitution
A functional group in a compound is replaced by another
Because a nucleophile attacked a partially positive carbon
What do haloalkanes react with to form alcohols
OH-
What do haloalkanes react with to form amines?
Ammonia (dissolved in ethanol)
How is ozone formed and where?
Oxygen radicals and O2
UV radiation from sun breaks down oxygen into O radicals
- stratosphere
Equation for formation of ozone in the stratosphere
hv
O2 —> O + O
O2 + O —> O3
Why is the ozone layer being constantly replaced
UC radiation can reverse formation of O3
O3—>O2 +O
O can react with O2 to replace it
Creates an equilibrium
How does the ozone layer protect against UV radiation
When Ozone breaks down it absorbed high frequency radiation which can be dangerous to humans it reaches the troposphere
What can Ozone in the troposphere cause? And why is it bad?
- photochemical smog when mixed with pollutants such as NO2
- this can cause respiratory problems
- is toxic to humans and animals
- can damage plants and materials
What can breakdown to become catalysts in breaking down ozone?
CFCs (ChloroFloroCarbons)
What order or bond strength are carbon-halogen bonds?
Stronger up the group because it has high bond enthalpy.
More reactive down group
How is the ozone layer being destroyed by CFCs and homogenous catalysis?
More CFCs are being produced so chlorine radicals from CFCs act as catalysts in the break down resulting in more being broken down than being replaced.
Cl +O3—>O2+ClO
ClO+O3—>Cl+2O2
What radicals destroy ozone?
Cl
NO
Halogen radicals from haloalkanes
Equation for parts per million to percentage
Divide by 100
Times by 1 000 000
What does visible light and ultra violet radiation do to electrons?
Electrons have fixed energy levels which when they are hit by the right amount of UV or visible light they can move up
Only specific frequencies if enough is absorbed bonds break forming radicals
What makes a MOLECULE polar
Shape and polarity of bonds
Imagine the molecule like an atom
What does a significant difference in electronegativity do to a covalent bond
Polarise it
What is a dipole
Difference in charge between the two atoms caused by a shift in electron density in the bond
What difference in electronegativity is significant enough for to make it polar?
Approx 0.4
