ib chemistry on resonance, delocalization and ozone destruction
TRANSCRIPT
httplawrencekokblogspotcom
Prepared by Lawrence Kok
Tutorial on Resonance Delocalization and catalytic destruction of Ozone
Delocalization of electron
Resonance structures ozone
resonance structure 1 resonance structure 2
resonance hybrid
bull All bond O-O are identical in length strengthbull Hybrid of 2 resonance structurebull NO O-O (single) or O=O (double) bonds foundbull Only O ----- O bondbull Intermediate in character bet single and double bond
bull Bond Order = 15
Ozone 3O
Click here on video ozone
Resonance bull Describe delocalization of elec within a moleculepolyatomic ion where bonding cant be express by ONE single Lewis structurebull Delocalization of π bond ndash π elec spread over more than 2 nucleibull π elec are sharedspread ndash more stable
bull Pale blue gas polar dimagneticbull Oxidizing agentbull Potent respiratory hazard pollutant at ground levelbull Beneficial prevent UV BC from reaching Earth bull Highest ozone level in stratosphere (10 km and 50 km)
Ozone at stratosphere
strongest radiation
UV radiation
FORMAL CHARGE (FC)
Formal ChargebullToolModel for comparing which Lewis structures is more acceptablebullTreat covalent bond with equal electron distribution no electronegativity differences bet atombullElectronegative atom has negative while least electronegative atom has positive formal charge
Formula formal charge
V - valence electrons of atom L ndash lone pair electronB ndash bonding electron moleculeFormal charge sulfur dioxide
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 4B- Bonding electron O = 4
L +
FC = 6 ndash (4 +2) = 0
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 6B- Bonding electron O = 2
FC = 6 ndash (6+1) = -1
formal charge for O
V- Valence electron O = 6L - Lone pair electron O = 2B - Bonding electron O = 6
FC = 6 ndash (2+3) = +1
All resonance structure contribute to electronic structure Real structure is combination of themLowest FC (stable) contribute more than less stable structureSum of FC must be zero for neutral or equal to charge on ion
0+1
-1
L + L + L +
Ozone Good and Bad
Ozone in Strastopherebull blocks UV B + C Ozone in Troposphere act as
bull Greenhouse gas
Ozone in ground level act as bullPollutant bullPhotochemical
Click here on ozone depletion substances ODS (phaseout)
Why ozone able to absorb UV B and UV C
Breakdown of ozone ndash High UV radiation ndash Skin cancer - DNA mutation
Ozone depletion
UV Exposure
Ozone Hole
Bad SideGood Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double bond
O=O=OInter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt 242nm
lt 330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230 nm)
Free radical -reactive species with unpair electron
How ozone layer protect life on earth
Ozone Cycle
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone cycle
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
O3 formation
O3 destruction
+
+
1
2
3
4
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Delocalization of electron
Resonance structures ozone
resonance structure 1 resonance structure 2
resonance hybrid
bull All bond O-O are identical in length strengthbull Hybrid of 2 resonance structurebull NO O-O (single) or O=O (double) bonds foundbull Only O ----- O bondbull Intermediate in character bet single and double bond
bull Bond Order = 15
Ozone 3O
Click here on video ozone
Resonance bull Describe delocalization of elec within a moleculepolyatomic ion where bonding cant be express by ONE single Lewis structurebull Delocalization of π bond ndash π elec spread over more than 2 nucleibull π elec are sharedspread ndash more stable
bull Pale blue gas polar dimagneticbull Oxidizing agentbull Potent respiratory hazard pollutant at ground levelbull Beneficial prevent UV BC from reaching Earth bull Highest ozone level in stratosphere (10 km and 50 km)
Ozone at stratosphere
strongest radiation
UV radiation
FORMAL CHARGE (FC)
Formal ChargebullToolModel for comparing which Lewis structures is more acceptablebullTreat covalent bond with equal electron distribution no electronegativity differences bet atombullElectronegative atom has negative while least electronegative atom has positive formal charge
Formula formal charge
V - valence electrons of atom L ndash lone pair electronB ndash bonding electron moleculeFormal charge sulfur dioxide
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 4B- Bonding electron O = 4
L +
FC = 6 ndash (4 +2) = 0
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 6B- Bonding electron O = 2
FC = 6 ndash (6+1) = -1
formal charge for O
V- Valence electron O = 6L - Lone pair electron O = 2B - Bonding electron O = 6
FC = 6 ndash (2+3) = +1
All resonance structure contribute to electronic structure Real structure is combination of themLowest FC (stable) contribute more than less stable structureSum of FC must be zero for neutral or equal to charge on ion
0+1
-1
L + L + L +
Ozone Good and Bad
Ozone in Strastopherebull blocks UV B + C Ozone in Troposphere act as
bull Greenhouse gas
Ozone in ground level act as bullPollutant bullPhotochemical
Click here on ozone depletion substances ODS (phaseout)
Why ozone able to absorb UV B and UV C
Breakdown of ozone ndash High UV radiation ndash Skin cancer - DNA mutation
Ozone depletion
UV Exposure
Ozone Hole
Bad SideGood Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double bond
O=O=OInter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt 242nm
lt 330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230 nm)
Free radical -reactive species with unpair electron
How ozone layer protect life on earth
Ozone Cycle
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone cycle
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
O3 formation
O3 destruction
+
+
1
2
3
4
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
FORMAL CHARGE (FC)
Formal ChargebullToolModel for comparing which Lewis structures is more acceptablebullTreat covalent bond with equal electron distribution no electronegativity differences bet atombullElectronegative atom has negative while least electronegative atom has positive formal charge
Formula formal charge
V - valence electrons of atom L ndash lone pair electronB ndash bonding electron moleculeFormal charge sulfur dioxide
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 4B- Bonding electron O = 4
L +
FC = 6 ndash (4 +2) = 0
formal charge for O
V- Valence electron O = 6L- Lone pair electron O = 6B- Bonding electron O = 2
FC = 6 ndash (6+1) = -1
formal charge for O
V- Valence electron O = 6L - Lone pair electron O = 2B - Bonding electron O = 6
FC = 6 ndash (2+3) = +1
All resonance structure contribute to electronic structure Real structure is combination of themLowest FC (stable) contribute more than less stable structureSum of FC must be zero for neutral or equal to charge on ion
0+1
-1
L + L + L +
Ozone Good and Bad
Ozone in Strastopherebull blocks UV B + C Ozone in Troposphere act as
bull Greenhouse gas
Ozone in ground level act as bullPollutant bullPhotochemical
Click here on ozone depletion substances ODS (phaseout)
Why ozone able to absorb UV B and UV C
Breakdown of ozone ndash High UV radiation ndash Skin cancer - DNA mutation
Ozone depletion
UV Exposure
Ozone Hole
Bad SideGood Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double bond
O=O=OInter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt 242nm
lt 330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230 nm)
Free radical -reactive species with unpair electron
How ozone layer protect life on earth
Ozone Cycle
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone cycle
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
O3 formation
O3 destruction
+
+
1
2
3
4
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Ozone Good and Bad
Ozone in Strastopherebull blocks UV B + C Ozone in Troposphere act as
bull Greenhouse gas
Ozone in ground level act as bullPollutant bullPhotochemical
Click here on ozone depletion substances ODS (phaseout)
Why ozone able to absorb UV B and UV C
Breakdown of ozone ndash High UV radiation ndash Skin cancer - DNA mutation
Ozone depletion
UV Exposure
Ozone Hole
Bad SideGood Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double bond
O=O=OInter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt 242nm
lt 330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230 nm)
Free radical -reactive species with unpair electron
How ozone layer protect life on earth
Ozone Cycle
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone cycle
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
O3 formation
O3 destruction
+
+
1
2
3
4
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double bond
O=O=OInter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt 242nm
lt 330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230 nm)
Free radical -reactive species with unpair electron
How ozone layer protect life on earth
Ozone Cycle
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone cycle
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
O3 formation
O3 destruction
+
+
1
2
3
4
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Ozone absorb UV radiation
Ozone formation
O=O O=O=O
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV
lt242nm
lt330nm
Ozone weaker bondbullAbsorb UV AB(wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bondbullAbsorb UV C (wavelength 230nm)
O2 split by high UV to O (radical)
O radical combine to form ozone
Ozone absorb UV BC
Ozone reform again
Ozone createddestroyed by Chapman cycle
Oxygen reform again
Weaker bond in ozone broken UV
Obull + O2 rarr O3
O3 + hv rarr O2 + Obull
O3 + Obull rarr 2O2
O2 + hv rarr 2Obull
Obull + O2 rarr O3
BE O3 = 363 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 363 kJ
Energy 1 photon - E = hf
In nature Ozone formation = Ozone destruction (without CFC free radical)
Velocity light (c) = frequency(f) x wavelength(λ) - c = f λbull Electromagnetic waves travel at speed of light (300 x 108ms-1)bull Radiation high uarr frequency ndash short darr wavelengthbull Electromagnetic radiationphoton- energy given by
E = hf hcE
h = plank constant = 6626 x 10-
34 Js f = frequency λ = wavelength
BE O2 = 498 kJmol-1
λ need to break O3 bondEnergy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 1923 10036
10026363000
nmEhc
33010036
1031063619
834
hcE
JE 1923 10278
10026498000
nmEhc
24110278
1031063619
834
hcE
easier to break harder to break
1
2
3
4
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Ozone absorb UV BC
CFC breaks down
How CFC breaks down
High UV BC
How CI radical destroy ozone
Catalytic destruction of ozone
Ozone Depleting Substances (ODS)
How CFC destroys ozone
CI free radicals form CImiddot react O3 form CIOmiddot radical
CIOmiddot react Omiddot form CImiddot radical
Net - ozone break down
CarbonFluorine
Chlorine
bullCI + O3 rarr bullCIO + O2
bullCIO + Obull rarr bullCI + O2
O3 + Obull rarr 2O2
+
F H ndash C ndash F CI
F F ndash C ndash CI CI
CI F ndash C ndash CI CI
Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
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Ozone absorb UV BC
NOx breaks down
How CFC breaks down
High UV BC
How NO radical destroy ozone
Catalytic destruction of ozone
NO free radicals form
NO react O3 form NO2 radical
NO2 react O form NO radical
Net - ozone break down
Oxides of Nitrogen
Nitrogen Dioxide (NO2)
Nitrogen monoxide (nitric
oxide NO)
Nitrous oxideN2O
Break down to form NO free radical (unpair electron)
Sources of NOx
NObull + O3 rarr NO2bull + O2
NO2bull + Obull rarr NObull + O2
O3 + Obull rarr 2O2
Ozone Depleting Substances (ODS)
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Catalytic destruction of ozone
Source of ODSbull Halogenated substancebull Man-made halocarbon refrigerant solvent propellantbull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like
carbon tetrachloride and trichloroethane
CFCbullContain chlorine fluorine atombullExtremely stable with strong bond long half lifebullStability allow CFC to stratosphere bullHigh UV radiation react with CFCbullHigh UV break CFC Free Cl radical form ndash destroy O3
Trichloroflouromethane CFC-11
Dichlorodifluoromethane CFC-12
Chlorodifluoromethane HCFC-22
Why halogenated CFC used
Less harmful
Very harmful
Why fluorinated is safer
CI F ndash C ndash CI CI
CI F ndash C ndash CI F
H F ndash C ndash CI F
Bond length
Bond strength
C ndash F 138 484
C ndash CI 176 338
C ndash Br 195 276
C ndash I 215 238
Ozone Depleting Substances (ODS)
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Conc O3 is shown below
i O2 rarr 2 O∙ii O2 + O∙ rarr O3
iii O3 rarr O2 + O∙
Identify which step is exothermic Step ii bond forming exothermic energy given off
With reference to bonding in O2 and O3 which step is most endothermicStep i and ii Bond breaking Step i O2 bond order 2 ndash strong bond ndash more energy
Step ii O3 bond order 15 ndash weak bond ndash less energy
Catalytic destruction of ozone
Ozone form from combustion of methaneCH4 (g) + 5 O2 (g) rarr CO2 (g) + 2 H2O (g) + 2O2 (g)
Find ∆H for rxn in kJ mol -1
= - 591 + 74 = - 517 kJ mol -1
Find ∆S in JK-1 mol-1
Find ∆G in kJ mol-1 at 298K
Deduce if rxn is spontaneous at 298K
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2O3 (g)
∆Hf 0 - 74 0 - 393 - 241
x 2 + 142 x 2
∆Hsysθ = sum∆Hf
θ(pro) - sum∆Hf
θ(react)
CH4(g) + 5 O2 (g) rarr CO2(g) + 2 H2O(g) + 2 O3 (g) S0 + 186 +205 x 5 + 213 + 188 x 2 + 237 x 2
- 74 - 591Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
GSTHG
1472 kJmolG
CCl2F2 cause ozone depletion Formulate eqn for each step and explain initial step by reference to bond in CCl2F2
CCI2F2 rarr ∙CCIF2 + CI∙
CI∙ + O3 rarr CIO∙ + O2
CIO ∙ + O∙ rarr O2 + CI∙
CIO∙ + O3 rarr 2O2 + CI∙
hv
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttpspaceplacenasagovgreenhouseenhttpwwwozonedepletioninfoeducationpart3ozonesourceshtmlhttpcreativecommonsorglicenseshttpwwwciesinorgdocs011-462011-462htmlhttpwwwepmagazineorgstorage165benzene-evidenceaspx
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttplawrencekokblogspotcom
- PowerPoint Presentation
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
-