Ozone Flashcards
how does sunscreen work
UV light is absorbed by a promoted e- then falls via thermal mechanism. Preventing uv from being absorbed by skin molecules and damaging them
explain the origin of the photochemical smog
UV light creates a mixture of hydrocarbons, ozone, NO and NO2
What were CFC’s used for?
CFC’s were used for refrigerants
why are termination reactions so slow
because radicals are in such low concentration
define electro negativity
ability of an atom to withdraw a pair of electrons from within a covalent bond
where does NO come from
particle combustion of nitrogen in car engines
where does OH come from
OH comes from free radical cleavage of water using uv
what is heterolytic fission
produces ions
e.g. H+ and Cl-
what is homolytic fission
produces radicals
eg. Br2 > Br• + Br•
conditions of haloalkane reactions
UV and 300°c
how are haloalkanes made
- from alkanes by substitution
- from alkenes by addition
- from alcohols
define a nucleophile
a molecule with a lone pair of e- that can be donated to a +vely charged atom to form a covalent bond
common nucleophiles are
OH- ion
CN- ion
H2O
how do ID - IDs work
the more protons (and e-) the bigger the dipole and the stronger the ID-ID forces (=higher bpt)
where does PD-PD bonding occur
in polar molecules
how strong is hydrogen bonding
very
C-Cl is a more polar bond than C-I this means the C-Cl bond is…
stronger
pd - pd forces stand for…
permanent dipole - permanent dipole
pd - pd forces arise due to…
differences in atoms electronegativity in a covalent bond causing electrostatic attractions
id - id forces stand for…
instantaneous dipole - induced dipole
id - id forces arise due to…
uneven distributions of electrons creating temporary dipoles that induce dipoles in their neighbouring molecules
pd - pd forces are stronger than…
but not….
id - id forces
H bonding
id - id are the weakest type of bond. true or false?
true
NOx pollution can cause….
acid rain
radicals have an…
unpaired electron
what makes a reaction a propagation reaction?
a radical is used and produced to continue the reaction
when nitrogen monoxide reaches the atmosphere what is seen?
colorless gas turns brown
a student predicts that C-Cl is more polar than C-I and therefore chloroethane will react faster than iodoethane. comment on this prediction
3 marks
- C-Cl is more polar than C-I
- however bond strength is more important and the C-Cl is stronger
- so the ppt forms faster with iodoethane
pd - pd forces arise due to…
differences in atoms electronegativity in a covalent bond
id - id forces arise due to…
uneven distributions of electrons creating temporary dipoles that induce dipoles in adjacent molecules
the main polluting effect of NO2 in the atmosphere is….
helps form acid rain
