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ozone story Flashcards

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1
Q

electronegativity definition

A

the ability for an atom to attract electrons towards itself in a covalent bond

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2
Q

electronegativity trend on periodic table

A

further up and further right you go, the more electronegative the element is (excluding group 8) i.e. fluorine is the most electronegative element

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3
Q

relationship between electronegativity and how ionic a compound is

A

the bigger the difference in electronegativity between molecules in a compound, the more ionic the compound will be
(a difference of zero will be purely covalent)

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4
Q

what are the intermolecular forces

A
  • instantaneous dipole - induced dipole
  • permanent dipole - permanent dipole
  • hydrogen bonds
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5
Q

features of instantaneous dipole - induced dipole bond

A
  • weakest type of imf
  • exist between all atoms and molecules, even if non-polar
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6
Q

process of formation of instantaneous dipole - induced dipole bond

A
  1. random movement of electron creates a temporary instantaneous dipole
  2. instantaneous dipole produces an induced dipole in a neighbouring molecule
  3. id-id forces are the temporary attraction between an instantaneous dipole on one molecule and an induced dipole in a neighbouring molecule
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7
Q

trends in instantaneous dipole - induced dipole forces

A
  • the strength of id-id forces increases with the polarisability of the molecule
  • bigger atoms = more electrons = stronger id-id forces = higher bpt
  • bigger molecule = more electrons = stronger id-id = higher bpt
  • straighter chain molecule = more id-id opportunities = overall stronger id-id = higher bpt
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8
Q

permanent dipole - permanent dipole features

A

significantly stronger than id-id forces

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9
Q

permanent dipole - permanent dipole bond criteria

A
  • must be polar (have electronegativity difference between atoms)
  • must not be symmetrical
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10
Q

features of hydrogen bonds

A

strongest intermolecular force

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11
Q

hydrogen bond criteria

A
  • O-H, F-H, or N-H bond in molecule
  • H also bonding to O,N or F on other side
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12
Q

reasoning for hydrogen bond criteria

A
  • O, N, F are the most electronegative elements so they can withdraw electrons, making H very partially positive
  • H must bond to O, N, or F on other side because they have lone pair of electrons which are directly involved in H bond
  • Hydrogen - because no inner electrons to shield nucleus when bonded to very electronegative element, the hydrogen nucleus is deshielded
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13
Q

hydrogen bonding in water

A
  • not all possible hydrogen bond form
  • molecules closer together
  • more dense
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14
Q

hydrogen bonding in ice

A
  • all 4 possible hydrogen bonds from to each water molecule
  • this pushes water molecules slightly further apart
  • open tetrahedral network
  • ice is less dense than water
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15
Q

trends going from id-id, pd-id, pd-pd, to hydrogen bonding

A
  • increase in strength of intermolecule force
  • more energy needed to overcome force
  • higher bpt, mpt, and viscosity
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16
Q

what is activation energy

A

Ea
the minimum energy required for a reaction to take place between two colliding reacting particles

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17
Q

what is an enthalpy profile

A

diagram showing enthalpy changes in a reaction

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18
Q

enthalpy profile for exothermic reaction

A

reactants higher than products

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19
Q

enthalpy profile for endothermic reaction

A

reactants lower than products

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20
Q

collision theory requirements for a reaction to occur

A

1 . successful collisions
2. energy > activation energy (achieved with temperature)

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21
Q

effect of concentration on rate of reaction

A
  • increase in concentration = more molecules of substance in the same volume = more closely packed together = collisions between molecules become more likely and probability of a collision occurring with energy greater than or equal to activation energy increases
    = rate of reaction increases
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22
Q

effect of pressure on rate of reaction

A
  • increase in pressure has similar effect as increase in concentration as molecules are packed close together in a smaller volume
  • rate of reaction increases
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23
Q

effect of increase in temperature on rate of reaction

A
  • thermal energy transferred to substance
  • converted to kinetic energy
  • molecules of substance move faster + further = increased movement of molecules = collisions occur more often and with greater energy
  • greater proportion of particles with an energy greater than the activation energy
  • increased rate of reaction
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24
Q

effect of catalyst on rate of reaction

A
  • catalyst lowers activation energy resulting in
  • large increase in proportion of particles with energy greater than activation energy
  • more frequent collisions with energy greater than activation energy
  • increase in rate of reaction
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25
Q

role of catalysts

A
  • increasing rate of reaction without being used up by providing an alternative reaction path with a lower activation energy
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26
Q

homogeneous catalyst meaning

A

catalysts that are in the same state as the reactants

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27
Q

working out the total volume of a mixture of gases

A

total volume of a mixture of gases = the sum of all the individual partial volumes in the mixture

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28
Q

converting between %volume and ppm

A

% – x10 to the power of 4 –> ppm

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29
Q

haloalkane functional groups

A

C - X
with X being a halogen

30
Q

naming haloalkanes

A

X - alkane
e.g. bromoethane
2 - chlorobutane

31
Q

amine functional group

A
  • NH2
32
Q

naming amines

A

(alkyl group) amine
e.g. methylamine
propylamine

33
Q

haloalkane boiling points

A

induced dipole forces increase from F to I haloalkanes due to increased number of electrons
boiling point increases as the number of C atoms in chain increases

34
Q

haloalkane reactivity series

A

increases going down the group
as bigger halogen, weaker bonds, easier to break, more reactive

35
Q

haloalkane + water nucleophilic substitution reaction

A

haloalkane + water –> alcohol

36
Q

haloalkane + water nucleophilic substitution reagents

A

water, ethanol cosolvent

37
Q

haloalkane + water nucleophilic substitution conditions

A

heat to reflux

38
Q

haloalkane + water nucleophilic substitution nucleophile

A

H2O:

39
Q

haloalkane + alkali nucleophilic substitution reaction

A

haloalkane + NaOH –> alcohol

40
Q

haloalkane + alkali nucleophilic substitution reagents

A

NaOH(aq), ethanol cosolvent

41
Q

haloalkane + alkali nucleophilic substitution conditions

A

heat to reflux

42
Q

haloalkane + alkali nucleophilic substitution nucleophile

A

:OH-

43
Q

haloalkane + ammonia nucleophilic substitution reaction

A

haloalkane + ammonia –> amine

44
Q

haloalkane + ammonia nucleophilic substitution reagent

A

concentrated NH3

45
Q

haloalkane + ammonia nucleophilic substitution conditions

A

heat in a sealed tube, high pressure and temperature

46
Q

haloalkane + ammonia nucleophilic substitution nucleophile

A

:NH3

47
Q

nucleophile definition

A

an electron pair doner

48
Q

substitution reaction definition

A

one functional group being replaced by a different functional group

49
Q

why is iodoalkane more reactive than fluoroalkane

A

the C-I bond has a higher bond enthalpy than the C-F bond

50
Q

heterolytic fission meaning

A

both electrons in bond move onto one atom
forms ions
more common in polar bonds + solvents
full curly arrow

51
Q

homolytic fission meaning

A

one electron in bond moves onto each atom
forms radicals
more common in non-polar solvents and gas phase
two curly half arrows

52
Q

radical definition

A

an atom or molecule with an unpaired electron

53
Q

radical chain reaction process

A
  1. initiation (molecules -> radicals, homolytic fission)
  2. propagation (radicals -> radicals, pairs of steps)
  3. termination (radicals -> molecules)
54
Q

what does a full headed arrow represent

A

two electrons moving

55
Q

what does a half head arrow represent

A

one electron moving away

56
Q

where do reactions of the ozone take place + why

A

reactions of ozone take place in the stratosphere, as in the stratosphere there is high energy u.v.

57
Q

formation of ozone reaction

A

a) O = O –h.e u.v–> 2O radical (g)
b) O2 (g) + O (g) –> O3 (g)

58
Q

depletion of ozone reaction

A

O3 (g) –h.e u.v –> O2(g) + O(g)

59
Q

formation + depletion of ozone naturally

A

steady, rate of formation = rate of depletion, concentration of ozone remains constant

60
Q

problem with ozone now

A

solar radiation causes haloalkanes that reach the stratosphere to split giving chlorine and bromine radicals

61
Q

chloroalkane depletion of ozone propagation steps

A

a) Cl radical(g) + O3(g) -> ClO radical (g) + O2(g)
b) ClO radical (g) + O(g) -> Cl radical (g) + O2(g)

62
Q

why do C-I molecules have no effect on ozone depletion

A

C-F bonds are the least likely to break, and C-I are the most likely
this is because C-F has the highest bond enthalpy and C-I the lowest
so most C-I bonds react before reaching the stratosphere, and thus have little effect on the ozone layer

63
Q

uses of the ozone

A

absorbs most high energy UV radiation, preventing it from reaching surface (acts as a sunscreen)

64
Q

effects of UV

A
  • can break DNA and damage genes
  • increases risk of skin cancer
  • damages proteins in skin, making people look older
65
Q

polluting effects of ozone in troposphere

A
  • photochemical smog -> leads to irritation and respiratory problems
  • ozone is tocis to humans
  • UV radiation is one of the main ways humans produce vitamin D
66
Q

radiation the sun emits, in order of increasing frequency

A
  • infrared
  • visible light
  • ultraviolet
67
Q

calculation to work out wavelength

A

wavelength (m) = speed of light / frequency (Hz)

68
Q

calculation to work out the energy of a photon

A

energy of a photon (J) = planck’s constant x frequency (Hz)

69
Q

calculation to work out bond enthalpy

A

bond enthalpy (kJmol-1) = energy of a photon (J) x avogadros constant

70
Q

photodissociation process

A
  • electrons in any molecule have fixed energy levels
  • electrons may be excited to a higher energy level when they absorb radiation
  • with even more energy, the bonding electrons will no longer be able to hold the bond and radicals will be formed (aka photodissociation)
  • ionisation is also possible if there is enough energy for an electron to leave
71
Q

what is the addition of energy from photons shortened to

A

+ hv

chemistry (8 decks)

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