ib chemistry on resonance, delocalization and ozone destruction
TRANSCRIPT
Delocalization of electron
Resonance structures ozone
resonance structure 1 resonance structure 2
resonance hybrid
bull All bond O-O are identical in length strength bull Hybrid of 2 resonance structure bull NO O-O (single) or O=O (double) bonds found bull Only O ----- O bond bull 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 structure bull Delocalization of π bond ndash π elec spread over more than 2 nuclei bull π elec are sharedspread ndash more stable
bull Pale blue gas polar dimagnetic bull Oxidizing agent bull Potent respiratory hazard pollutant at ground level bull 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 Charge bull ToolModel for comparing which Lewis structures is more acceptable bull Treat covalent bond with equal electron distribution no electronegativity differences bet atom bull Electronegative atom has negative while least electronegative atom has positive formal charge
Formula formal charge
V - valence electrons of atom L ndash lone pair electron B ndash bonding electron molecule
Formal charge sulfur dioxide
formal charge for O
V- Valence electron O = 6 L- Lone pair electron O = 4 B- Bonding electron O = 4
L +
FC = 6 ndash (4 +2) = 0
formal charge for O
V- Valence electron O = 6 L- Lone pair electron O = 6 B- Bonding electron O = 2
FC = 6 ndash (6+1) = -1
formal charge for O
V- Valence electron O = 6 L - Lone pair electron O = 2 B - Bonding electron O = 6
FC = 6 ndash (2+3) = +1
All resonance structure contribute to electronic structure Real structure is combination of them Lowest FC (stable) contribute more than less stable structure Sum 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 Strastophere bull blocks UV B + C
Ozone in Troposphere act as bull Greenhouse gas
Ozone in ground level act as bull Pollutant bull Photochemical
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 Side Good Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double
bond
O=O=O Inter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV lt 242nm lt 330nm
Ozone weaker bond bull Absorb UV AB (wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond bull Absorb UV AB (wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond Energy 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 λ bull Electromagnetic waves travel at speed of light (300 x 108ms-1) bull Radiation high uarr frequency ndash short darr wavelength bull 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 bond Energy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 19
2310036
10026
363000
nm
E
hc
330
10036
1031063619
834
hcE
JE 19
2310278
10026
498000
nm
E
hc
241
10278
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
FORMAL CHARGE (FC)
Formal Charge bull ToolModel for comparing which Lewis structures is more acceptable bull Treat covalent bond with equal electron distribution no electronegativity differences bet atom bull Electronegative atom has negative while least electronegative atom has positive formal charge
Formula formal charge
V - valence electrons of atom L ndash lone pair electron B ndash bonding electron molecule
Formal charge sulfur dioxide
formal charge for O
V- Valence electron O = 6 L- Lone pair electron O = 4 B- Bonding electron O = 4
L +
FC = 6 ndash (4 +2) = 0
formal charge for O
V- Valence electron O = 6 L- Lone pair electron O = 6 B- Bonding electron O = 2
FC = 6 ndash (6+1) = -1
formal charge for O
V- Valence electron O = 6 L - Lone pair electron O = 2 B - Bonding electron O = 6
FC = 6 ndash (2+3) = +1
All resonance structure contribute to electronic structure Real structure is combination of them Lowest FC (stable) contribute more than less stable structure Sum 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 Strastophere bull blocks UV B + C
Ozone in Troposphere act as bull Greenhouse gas
Ozone in ground level act as bull Pollutant bull Photochemical
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 Side Good Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double
bond
O=O=O Inter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV lt 242nm lt 330nm
Ozone weaker bond bull Absorb UV AB (wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond bull Absorb UV AB (wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond Energy 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 λ bull Electromagnetic waves travel at speed of light (300 x 108ms-1) bull Radiation high uarr frequency ndash short darr wavelength bull 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 bond Energy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 19
2310036
10026
363000
nm
E
hc
330
10036
1031063619
834
hcE
JE 19
2310278
10026
498000
nm
E
hc
241
10278
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
Ozone Good and Bad
Ozone in Strastophere bull blocks UV B + C
Ozone in Troposphere act as bull Greenhouse gas
Ozone in ground level act as bull Pollutant bull Photochemical
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 Side Good Side
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double
bond
O=O=O Inter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV lt 242nm lt 330nm
Ozone weaker bond bull Absorb UV AB (wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond bull Absorb UV AB (wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond Energy 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 λ bull Electromagnetic waves travel at speed of light (300 x 108ms-1) bull Radiation high uarr frequency ndash short darr wavelength bull 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 bond Energy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 19
2310036
10026
363000
nm
E
hc
330
10036
1031063619
834
hcE
JE 19
2310278
10026
498000
nm
E
hc
241
10278
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
Ozone absorb UV radiation
Ozone absorb UV BC
Ozone formation
O=O Double
bond
O=O=O Inter
mediate
Bond lengthpm 121 127
Bond enthalpykJ mol-1
498 363
Bond order 2 15
Dissociation by UV lt 242nm lt 330nm
Ozone weaker bond bull Absorb UV AB (wavelength 330 nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond bull Absorb UV AB (wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond Energy 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 λ bull Electromagnetic waves travel at speed of light (300 x 108ms-1) bull Radiation high uarr frequency ndash short darr wavelength bull 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 bond Energy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 19
2310036
10026
363000
nm
E
hc
330
10036
1031063619
834
hcE
JE 19
2310278
10026
498000
nm
E
hc
241
10278
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
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 bond bull Absorb UV AB (wavelength 330nm)
Bonding O2 and O3
Oxygen stronger bond bull Absorb 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 bond Energy 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 λ bull Electromagnetic waves travel at speed of light (300 x 108ms-1) bull Radiation high uarr frequency ndash short darr wavelength bull 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 bond Energy 1 mole 602 x 1023 = 498 kJ
Energy 1 photon - E = hf
JE 19
2310036
10026
363000
nm
E
hc
330
10036
1031063619
834
hcE
JE 19
2310278
10026
498000
nm
E
hc
241
10278
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
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
Carbon
Fluorine
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
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 oxide N2O
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 ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
Catalytic destruction of ozone
Source of ODS bull Halogenated substance bull Man-made halocarbon refrigerant solvent propellant bull Foam-blowing agent (CFC HCFC freon halon)
Montreal Protocol ban CFC halon and ODS like carbon tetrachloride and trichloroethane
CFC bull Contain chlorine fluorine atom bull Extremely stable with strong bond long half life bull Stability allow CFC to stratosphere bull High UV radiation react with CFC bull High 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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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
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 endothermic Step 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 methane CH4 (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 - 591 Reactant Product
1
)tan()(
148
12111063
JKS
S
SSS
sys
sys
treacproductsys
+ 1211 + 1063 Reactant Product
syssyssys STHG
1472
)1480(298517
kJmolG
G
STHG
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