ozone

Question 1

define heterolytic fission

Answer 1

the breaking of a covalent bond in which one atom takes both electrons from the shared pair, forming an anion and a cation

Question 2

define homolytic fission

Answer 2

the breaking of a covalent bond in which each atom takes one electron from the shared pair, forming two radicals

Question 3

what influences the amount of energy needed to break a bond either heterolytically or homolytically

Answer 3

bond enthalpy

Question 4

define a radical

Answer 4

a species with an unpaired electron, making it highly reactive

Question 5

why are radicals highly reactive

Answer 5

they want to pair up that electron

Question 6

what are two examples of radicals which arent highly reactive

Answer 6

NO2 and NO, not all radicals are highly reactive

Question 7

what type of reactions does a radical participate in

Answer 7

radical chain reactions

Question 8

what are the three stages in a radical chain reaction

Answer 8

initiation, propagation and termination

Question 9

what happens during inititation

Answer 9

UV light from sunlight provides energy to break a covalent bond (photodissociation) homolytically, producing two radicals

Question 10

1)write the initiation equation for the formation of chlorine radicals

Answer 10

Cl2(g) + hv -> Cl⋅ + Cl⋅

Question 11

what does hv represent

Answer 11

UV light

Question 12

what happens during propagation

Answer 12

radicals react with molecules(or radicals) and produce more radicals

Question 13

2) what does the chlorine(halogen) radical attack

Answer 13

the alkane
Cl⋅ + CH4 −> HCl + CH3⋅(intermediate)

Question 14

3) what does the alkyl radical attack

Answer 14

a chlorine molecule
CH3⋅ + Cl2 −> CH3Cl + Cl⋅

Question 15

4) what does the chlorine radical produced here do

Answer 15

it attacks another CH4 molecule and so on till all the Cl2 and CH4 molecules are wiped out, the chlorine radical is regenerated

Question 16

what happens during termination

Answer 16

Two radicals combine to form a stable molecule

Question 17

what could cause the reaction to go on even though termination occurs

Answer 17

initiation could be producing them faster than termination consumes them

Question 18

what could cause the reaction to stop even though initiation occurs

Answer 18

termination could be consuming radicals quicker than initiation produces them

Question 19

if there are a small amount of radicals, can they still get rid of all the chlorine and methane

Answer 19

yes, they never get used up, they can only be terminated

Question 20

5)write three termination equations for alkyl and chlorine radicals

Answer 20

Cl⋅ + Cl⋅ −> Cl2
CH3⋅ + Cl⋅ −> CH3Cl
CH3⋅ + CH3⋅ −> C2H6

Question 21

what type of arrows do we use in radical chain reactions

Answer 21

half curly arrows

Question 22

what does one half curly arrow represent

Answer 22

1 electron

Question 23

NOTE: make sure u draw out the radical chain reactions with the arrows

Question 24

where is the ozone layer

Answer 24

in the stratosphere

Question 25

how is ozone(In the stratosphere) formed

Answer 25

when UV light in sunlight hits oxygen molecules

Question 26

what four things does ozone absorbing UV to break down protect us from

Answer 26

-damage in our DNA -skin cancer -eye damage -immune system supression

Question 27

whats one thing that humans need UV for

Answer 27

vitamin D

Question 28

1)write the initiation reaction for the formation of chlorine radicals from CFCS

Answer 28

CCl3F + hv -> CCl2F(g) + Cl⋅(g) (they could also form from the photodissociation of Cl2)

Question 29

2) write the propagation reaction for the chlorine radical attacking ozone

Answer 29

Cl⋅(g) + O3(g) -> O2(g) + ClO⋅(g), the intermediate

Question 30

3) write the propagation reaction for the ClO⋅ attacking an oxygen atom

Answer 30

ClO⋅(g) + O⋅(g) -> O2(g) + Cl⋅(g) the chlorine radical is regenerated

Question 31

how was the oxygen radical formed

Answer 31

when hv breaks down O2 via photodissociation

Question 32

how come two radicals are reacting? doesnt the radical react with a molecule during propagation

Answer 32

Radical + radical = termination only if no new radicals are produced

Question 33

4) write the termination reactions

Answer 33

ClO⋅ + ClO⋅ -> Cl2O2 Cl⋅ + Cl⋅ −> Cl2 Cl⋅+ClO⋅ −> Cl2O

Question 34

what three environmental effects does ozone have

Answer 34

-damage to plants, causes leaf damage -contributes to photochemical smog, brown haze is formed in cities -its a greenhouse gas which contributes to global warming

Question 35

what are two examples of homogenous catalysts

Answer 35

chlorine and bromine radicals

Question 36

how do we work out the overall reaction equation for a radical chain reaction

Answer 36

you add up the propagation steps and cancel anything that appears on both sides

Question 37

What’s overall equation for the breakdown of ozone work it out urself first

Answer 37

O3 + O -> 2O2