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Chemistry Essentials - 053
Enthalpy of Reaction
Alfred Nobel
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!!!
Surroundings
Enthalpy of Reaction
Endothermic
Reactants
Bond Energies - Bond Energies
Exothermic
Thermal EnergyThermal Energy
Products Hess’s Law
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Exothermic reaction
Energy Diagram
Reaction Progress
Ener
gy
The
rmite
Reactants
Products
Fe2O3 + 2Al 2Fe + Al2O3
ΔH
ΔH = H(products) - H(reactants)
ΔH = -850kJ/mol
Enthalpy of reaction
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Enthalpy DiagramEn
thal
py
The
rmite
Fe2O3 + 2Al 2Fe + Al2O3
ΔH= -850 kJ/mol
Fe2O3 + 2Al
2Fe + Al2O3
Enthalpy
Reactants
Enthalpy
Products
ΔH = H(products) - H(reactants)bozemanscience.com
Enthalpy Diagram
Fe2O3 + 2Al 2Fe + Al2O3
Fe2O3 + 2Al
2Fe + Al2O3
Enthalpy
Reactants
Enthalpy
Products
Enth
alpy
ΔH= 850 kJ/mol
ΔH = H(products) - H(reactants)bozemanscience.com
Enthalpy DiagramEn
thal
py
The
rmite
Fe2O3 + 2Al 2Fe + Al2O3
ΔH= -850 kJ/mol
Fe2O3 + 2Al
2Fe + Al2O3
Enthalpy
Reactants
Enthalpy
Products
ΔH = H(products) - H(reactants)
Hess’s Law !
!
Reverse reaction - Reverse sign
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Endothermic reaction
Energy Diagram
Reaction Progress
Ener
gy
Am
mon
ium
nitr
ate
Reactants
Products
NH4NO3(s) NH4+(aq) + NO3-(aq)ΔH
ΔH = H(products) - H(reactants)
ΔH = 365kJ/mol
Enthalpy of reaction
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Enthalpy Diagram
Am
mon
ium
nitr
ate
NH4NO3(s) NH4+(aq) + NO3-(aq)
NH4NO3(s)
NH4+(aq) + NO3-(aq)
Enthalpy
Reactants
Enthalpy
Products
ΔH = H(products) - H(reactants)
ΔH= 365 kJ/mol
Enth
alpy
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Li(s)
F2(g)LiF(s)
Born–Haber cycle
Hess’s Law !
!
Enthalpy of reaction is equal to the sum of the parts
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C(s)
Hess’s Law
!
!
Reverse sign The sum of the parts
+ O2(g) CO2(g) ΔH = -393.5 kJ
CO(g) +½O2(g) CO2(g) ΔH = -283.0 kJ
C(s) ½O2(s) CO(g)+Target
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C(s)
Hess’s Law
!
!
Reverse sign The sum of the pars
+O2(g) CO2(g) ΔH = -393.5 kJ
CO(g)+½O2(g)CO2(g) ΔH = 283.0 kJ
C(s) ½O2(s) CO(g)+Target
C(s) CO(g)+½O2(g) ΔH = -110.5 kJ
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NO(g)+O3(g) NO2(g) ΔH = -198.9 kJ
NO(g) O(g) NO2(g)+Target
+ O2(g)O3(g) ΔH = -142.3 kJO2(g)3
2
O2(g)ΔH = -142.3 kJ
2O(g) ΔH = 495.0 kJ
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NO(g)+O3(g) NO2(g) ΔH = -198.9 kJ
NO(g) O(g) NO2(g)+Target
+ O2(g)O3(g) ΔH = 142.3 kJO2(g)3
2
O2(g)2O(g) ΔH = -495.0 kJ
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NO(g)+O3(g) NO2(g) ΔH = -198.9 kJ
NO(g) O(g) NO2(g)+Target
+ O2(g)O3(g) ΔH = 142.3 kJO2(g)3
2
O2(g)2O(g) ΔH = -495.0 kJ½( )
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NO(g)+O3(g) NO2(g) ΔH = -198.9 kJ
NO(g) O(g) NO2(g)+Target
+ O2(g)O3(g) ΔH = 142.3 kJO2(g)3
2
½O2(g)O(g) ΔH = -247.5 kJ
NO(g)+ O(g) NO2(g) ΔH = -304.1 kJ
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To draw qualitative and quantitative patterns in reaction enthalpy and the energies involved in
breaking and forming chemical bonds. !
Did you learn? Enthalpy of Reaction
Reactants
Bond Energies - Bond Energies
Products
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Dnn87. Pieces of Lithium Metal from the Dennis S.k Collection, 12/12-07. Self-photographed. http://commons.wikimedia.org/wiki/File:Limetal.JPG. “File:AlfredNobel Adjusted.jpg,” December 16, 2013. http://en.wikipedia.org/wiki/File:AlfredNobel_adjusted.jpg. “File:Dynamite-5.svg,” December 16, 2013. http://en.wikipedia.org/wiki/File:Dynamite-5.svg. “File:Hess Germain Henri.jpg,” December 22, 2013. http://en.wikipedia.org/wiki/File:Hess_Germain_Henri.jpg. “File:Nitroglycerin-3D-vdW.png,” December 16, 2013. http://en.wikipedia.org/wiki/File:Nitroglycerin-3D-vdW.png. “File:ThermiteReaction.jpg,” December 11, 2013. http://en.wikipedia.org/w/index.php?title=File:ThermiteReaction.jpg&oldid=543297076. Haacken, User: Herbert. English: Instant Cold Pack, March 15, 2012. Own work: Herbert Haacken. http://commons.wikimedia.org/wiki/File:2012-03-15_Ruck-Zuck-Pack_K%C3%A4lte_Katalog_Small.gif. V1adis1av. Single Crystal of Lithium Fluoride, LiF, in a Beaker with Water, March 20, 2008. Own work. http://commons.wikimedia.org/wiki/File:LiF-crystal.jPeG.
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