oz

Question 1

what is the atmosphere composed of?

Answer 1

troposphere (where we Trek)
stratosphere (where Stars are)

Question 2

how do you calculate the composition?

Answer 2

(m/mr)x100

pph to ppm
x10000

Question 3

what effect does the sun have on the skin?

Answer 3

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

Question 4

what are the behavioural aspects of light?

Answer 4

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

Question 5

3 things that happen when a molecule absorbs UV-VIS radiation:

Answer 5

> 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

Question 6

how do you calculate the speed of light?

Answer 6

speed of light = wavelength x frequency
ms-1 = m x s-1

Question 7

what are the 2 main types of bond fission?

Answer 7

heterolytic
homolytic

Question 8

what is heterolytic fission?

Answer 8

both electrons shared go to to just one atom when the bond breaks
this atom is more -ivly charged and the other more +ive

Question 9

when is heterolytic fission common?

Answer 9

when the bond is already polar

Question 10

what is homolytic fission?

Answer 10

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

Question 11

when are radicals most commonly formed from heterolytic fission?

Answer 11

when the atom is non-polar

Question 12

why are radicals so reactive?

Answer 12

because they fill their outer shells by grabbing an electron from other molecules/atoms

Question 13

what are the three key stages of a radical chain reaction?

Answer 13

Initiation = radicals only in products
Propagation(x2) = radicals in both products and reactants
Termination = radicals in only reactants

Question 14

factors effecting the rates of reaction?

Answer 14

temperature
catalysts
surface area
pressure/concentration
intensity of radiation

Question 15

how does temperature effect the rates of reactions?

Answer 15

increasing temp will increase rates because particles will have greater kinetic energy = more frequent successful collisions

Question 16

how can effects of temp on a reaction be shown?

Answer 16

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

Question 17

how do catalysts affect the rates of reactions?

Answer 17

provides alternative pathway with a Lowe activation enthalpy so more particles will have sufficient energy to react upon collision increasing rate of reactions

Question 18

how does surface area affect rates of reaction?

Answer 18

increasing SA will increase the area in which particles can collide in and so more frequent successful collisions can take place

Question 19

how does conc/pressure affect rates of reactions?

Answer 19

increasing c+p will increase increases number of particles in a given volume increasing rate of reaction as more frequent successful collisions

Question 20

hoe does the intensity of radiation effect the rate of reaction?

Answer 20

dissociation of molecules will happen faster is radiation is involved

Question 21

how can rates of reaction be measured?

Answer 21

measuring volume of gas produced
measuring mass change
pH measurements
colorimetry
chemical analysis and titration (involves quenching)

Question 22

what is ozone layer made up of?

Answer 22

O3

Question 23

what chemicals break down the ozone layer?

Answer 23

CFC’s (any element containing C, F, Cl)
they’re used in aerosol/fridge air conditioning/cleaning solvents

Question 24

depletion of the ozone layer: Cl atoms

Answer 24

CF3Cl —> CF3* + Cl*
Cl* + O3 —> ClO* + O2
ClO* + O3 —> Cl* + 2O2
ClO* + ClO* —> Cl2O2
overall : 2O3 —> 3O2

Question 25

what are the physical properties of haloalkanes?

Answer 25

properties and reactions of haloalkanes is determined by the polar C-H bonds

Question 26

the mole - gas calculations

Answer 26

number of moles= volume(dm3)/molar gas volume(dm3mol-1)

Question 27

under standard conditions what is the molar gas volume?

Answer 27

24dm3mol-1

Question 28

electronegativity?

Answer 28

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

Question 29

how do covalent bonds become polar?

Answer 29

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

Question 30

what is the order of IMF strongest to weakest?

Answer 30

hydrogen bonds
permanent dipole-perminant dipole
instantaneous dipole-induced dipole

Question 31

how do id-id form?

Answer 31

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

Question 32

what are some properties of id-id?

Answer 32

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

Question 33

what are properties of id-id in hydrocarbons?

Answer 33

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

Question 34

where do pd-pd IMF exist?

Answer 34

between polar molecules
therefore stronger then id-id

Question 35

what are some properties of pd-pd?

Answer 35

they’re weak electrostatic forces of attraction existing between polar molecules
molecules that have pd-pd also have id-id

Question 36

where does hydrogen bonding occur?

Answer 36

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

Question 37

what are some properties of hydrogen bonding?

Answer 37

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

Question 38

why does HF have a higher boiling point then HCl?

Answer 38

because hf has hydrogen n=bonding due to large electronegativity
more energy is needed to overcome the electrostatic forces