The Ozone Story
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Define electro negativity
The ability of an atom to attract the bonding electrons in a covalent bond
How are pola covalent bonds formed?
Atoms with different electro negativity, electrons attracted to the more electronegative atom more So they are spread unevenly
What does the polarity of a molecule depend on?
It’s shape- if symmetrical it is non polar
Name the 3 intermolecular bonds in order of strength getting stronger
Instantaneous dipole- indices dipole bonds Permanent dipole-permanent dipole bonds Hydrogen bonding
Which atoms have stronger ID-ID bonds?
The heavier- bigger atoms as they have more electrons
What two factors influence the boiling point of organic molecules? And why?
Length of the chain - longer means stronger idid bonds as more molecular surface contact Branching - less branching means more surface contacts so more Idid bonds form
What atoms does hydrogen bonding form between?
Hydrogen and either fluorine, nitrogen or oxygen
Why is ice less dense than water?
Water molecules are arranged for maximum number of hydrogen bonds so form a lattice As these bonds get broken, lattice breaks down and ice melts
What is activation energy?
Energy pairs of molecules need to react when they collide
What do catalysts do increase rate of reaction?
Provide an alternative reaction pathway with a lower activation energy
What is a homogeneous catalyst and how does it work?
Catalyst at same state as reactants They work by forming intermediate compounds with the reactants then the product is formed from this Overall needs a lower activation energy
What is the trend of boiling points of haloalkanes?
Boiling point increases down the group Atomic radius of halogens increase down the group leading to stronger IDID bonds More energy needed to overcome
What is formed when a haloalkane undergoes nucelophillic substitution with hydroxide ions, water and ammonia?
Alcohol + halogen ion Alcohol +halogen ion + hydrogen ion Amine + ammonia/ammonium
What is the trend in reactivities of haloalkanes?
Reactivity increases down the group Bond enthalpy decreases down group- needs to b broken for reaction due to smaller atomic radius
Define heterolytuc fission and where does it occur?
Uneven split of electrons - due to different electronegativity
Define homolytic fission and where does it occur?
Even split of electrons within a bond forming radicals Happens in molecules of a single atom and often in gases in stratosphere due to UV by photodidsociation
What acts as catalysts in the catalytic cycle of the breakdown of ozone and how is it formed?
Halogen radicals and other radicals Formed by photodissociation
What are the effects of ozone in the stratosphere?
Absorb high energy uv light Without cancer
What are the effects of ozone in the troposphere?
Photochemical smog and respiratory problems
What can uv and visible light do to electrons?
Promote to higher energy levels
explain the meaning of a propogation reaction?
when radicals react to produce new radicals to continue the reaction