OZ Flashcards
how can a covalent bond become polar
if there is a difference in electronegativity between the two atoms. the bigger the difference in electronegativity the more polar the bond will be
how are instantaneous dipole-induced dipoles formed
when a molecule’s electrons shift to one side one side will be slightly delta negative. when this molecule goes near another molecule, the new molecule will also have a delta positive and negative. when these two molecules move away from each other, the dipole is destroyed
permanent dipole-permanent dipole
occurs when there is a polar molecule, so a difference in electronegativity between the two atoms. eg HCL
hydrogen bonding
strongest type of intermolecular bonding. occurs when hydrogen on one molecule bonds with a nitrogen, oxygen or fluorine (3 most electronegative elements).
define rate of a reaction
change of concentration/ amount of a reactant or product per unit time
activation energy
minimum amount of energy required for a reaction to occur
in a maxwell-boltsmann graph, what are the two axis?
.number of particles = y axis
.kinetic energy = x axis
what happens to the particles when you increase heat
.more collisions occur as particles have more kinetic energy
.larger proportion of molecules have the minimum activation energy required to react
what affects rate of reaction (apart from temperature)
pressure - particles are closer together so more frequent collisions
concentration - greater quantity of particles so collisions are more frequent
homogenous catalyst
catalyst that is the same state as reactants
how can rate be measured experimentally
- use white paper and place a cross on it
- time how long it takes for precipitate to form (how long it takes for white cross to disappear)
. you can also measure rate of reaction of gas by timing how long it takes for gas to be produced using a gas syringe
what are haloalkanes
alkanes with a halogen (s) attached to it
boiling trends in haloalkanes and why
increase down the group because of the increasing number of electrons - more idid, meaning the strength of the intermolecular bond is greater
nucleophile
electron pair donor, eg H20, ammonia, OH-
nucleophilic substitution
when an electron pair donor (eg OH-) displaces an electrophile in a compound through substitution.
haloalkane reactivity
increases as you go down the group
heterolytic fission
bond breaks and electrons are distributed unequally to form 2 different ions (cation and anion)
homolytic fission
bond breaks with the pair of electrons in the bond being shared equally to form two uncharged radicals
initiation reaction
radicals are produced using uv light or visible light. the bond breaks homolytically
propagation reaction
chain reaction where a radical reacts with a non radical. new radicals are created and go on to react with other non radicals
termination reaction
two radicals reacting to form a non radical, thus ending the chain reaction.
how is bromomethane made from a free radical substitution
. initiation - two bromine radicals formed
. propagation - bromine radical reacts with CH3 molecule to produce CH3 radical - this new radical reacts with a BR2 molecule forming bromomethane and a bromine radical. this new bromine radical can react with another CH3 molecule
. termination - two radicals react to form a non radical eg bromomethane
what is a CFC
molecules that have had all their hydrogens replaced by fluorine and chlorine. they are stable molecules but are broken down by uv.
how is ozone formed
.ozone is formed when uv radiation from the sun hits oxygen molecules in the stratosphere (upper level of atmosphere).
. UV is absorbed by O2 molecules to form O radicals
. these O radicals react with O2 molecules to form O3
how is ozone broken
the O3 can react with uv radiation (hv) to form O2 and O. this O2 and O can react again to reform ozone - it is a reversible reaction
what is photchemical smog
when there is a mix of carbon particulates and ozone
affects of photchemical smog and ozone on wildlife
.photchemical smog harms respiratory system in animals and damages plants
.ozone is toxic to humans
equation linking energy, wavelength, plancks constant and speed of light
E = (hc) / wavelength
e = energy in j
h= plancks constant
c = speed of light
wavelength = metres
