oz Flashcards
what is the atmosphere composed of?
troposphere (where we Trek)
stratosphere (where Stars are)
how do you calculate the composition?
(m/mr)x100
pph to ppm
x10000
what effect does the sun have on the skin?
causes sunburn
= sun emits electromagnetic radiation
= the high energy can cause the chemical bonds in DNA to break and leading to damage in genes = skin cancer
what are the behavioural aspects of light?
translational (considered to be continuous)
rotational (caused by microwave radiation)
vibration of the bonds (caused by IR radiation)
electronic (caused by visible and UV radiation)
*increase in energy T = lease and E with most
all of these types of energy can be quantised (fixed levels) - occupy certain energy levels and can absorb distinct amounts of energy to move between these levels
3 things that happen when a molecule absorbs UV-VIS radiation:
> electrons are excited to higher energy levels then return to ground state
photodissociation - energy absorbed is enough to break bonds and radicals are formed
ionisation - enough energy is absorbed that an electron is able to leave the molecule and form an ion
how do you calculate the speed of light?
speed of light = wavelength x frequency
ms-1 = m x s-1
what are the 2 main types of bond fission?
heterolytic
homolytic
what is heterolytic fission?
both electrons shared go to to just one atom when the bond breaks
this atom is more -ivly charged and the other more +ive
when is heterolytic fission common?
when the bond is already polar
what is homolytic fission?
one of the two shared electrons goes to each atom involved
atom has no overall charge because the electronic structure hasn’t changed
radicals are formed
when are radicals most commonly formed from heterolytic fission?
when the atom is non-polar
why are radicals so reactive?
because they fill their outer shells by grabbing an electron from other molecules/atoms
what are the three key stages of a radical chain reaction?
Initiation = radicals only in products
Propagation(x2) = radicals in both products and reactants
Termination = radicals in only reactants
factors effecting the rates of reaction?
temperature
catalysts
surface area
pressure/concentration
intensity of radiation
how does temperature effect the rates of reactions?
increasing temp will increase rates because particles will have greater kinetic energy = more frequent successful collisions
how can effects of temp on a reaction be shown?
Maxwell-boltzmann distribution curve
- at higher temp a larger proportion of particles have the energy to collide which is shown via a more gradual and less steep curve compared to lower temps
how do catalysts affect the rates of reactions?
provides alternative pathway with a Lowe activation enthalpy so more particles will have sufficient energy to react upon collision increasing rate of reactions
how does surface area affect rates of reaction?
increasing SA will increase the area in which particles can collide in and so more frequent successful collisions can take place
how does conc/pressure affect rates of reactions?
increasing c+p will increase increases number of particles in a given volume increasing rate of reaction as more frequent successful collisions
hoe does the intensity of radiation effect the rate of reaction?
dissociation of molecules will happen faster is radiation is involved
how can rates of reaction be measured?
measuring volume of gas produced
measuring mass change
pH measurements
colorimetry
chemical analysis and titration (involves quenching)
what is ozone layer made up of?
O3
what chemicals break down the ozone layer?
CFC’s (any element containing C, F, Cl)
they’re used in aerosol/fridge air conditioning/cleaning solvents
depletion of the ozone layer: Cl atoms
CF3Cl —> CF3* + Cl*
Cl* + O3 —> ClO* + O2
ClO* + O3 —> Cl* + 2O2
ClO* + ClO* —> Cl2O2
overall : 2O3 —> 3O2
what are the physical properties of haloalkanes?
properties and reactions of haloalkanes is determined by the polar C-H bonds
the mole - gas calculations
number of moles= volume(dm3)/molar gas volume(dm3mol-1)
under standard conditions what is the molar gas volume?
24dm3mol-1
electronegativity?
ability for an atom to ATTRACT ELECTRONS towards itself in a COVALENT BOND
(the further up and right you go on the PT the more electronegative the element is = F is the most) excluding noble gases
how do covalent bonds become polar?
covalent bonds can become polar if the atoms attached have a difference in electronegativity
e.g c-cl
cl is more electronegative and so pulls the e- towards itself
what is the order of IMF strongest to weakest?
hydrogen bonds
permanent dipole-perminant dipole
instantaneous dipole-induced dipole
how do id-id form?
id-id can form in any molecule with electrons when they move near another molecule/atom
this is because e- in a molecule can move from one end to another = creating temporary dipoles
the s+ in one molecule will be attracted to the s- in another = force of attraction is created
what are some properties of id-id?
the bigger the molecule/atom the more instantaneous dipole-induced dipole forces there are as you have larger e- clouds
it is these bonds that are broken when a liquid is boiled not covalent bonds
what are properties of id-id in hydrocarbons?
longer, straight chain hydrocarbons have more id-id forces and so more energy is needed to overcome them = boiling point increases
branched hydrocarbons can’t pack as tightly and so their id-id forces are weakened = lower boiling point
where do pd-pd IMF exist?
between polar molecules
therefore stronger then id-id
what are some properties of pd-pd?
they’re weak electrostatic forces of attraction existing between polar molecules
molecules that have pd-pd also have id-id
where does hydrogen bonding occur?
occurs between very electronegative elements (oxygen, fluorine or nitrogen = most electronegative)
must be a large dipole
must be a hydrogen atom that can be close to the electronegative element (e.g O2, F, N)
must be a lone pair of electrons on the electronegative element
what are some properties of hydrogen bonding?
theyre the strongest IMB
the hydrogen on the molecule forms a bond with the lone pair of either O2, F or N
also have pd-pd and id-id
why does HF have a higher boiling point then HCl?
because hf has hydrogen n=bonding due to large electronegativity
more energy is needed to overcome the electrostatic forces
