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Chapter 5:. Thermochemistry. Thermochemistry:. Energy Kinetic & Potential First Law of Thermo internal energy, heat & work endothermic & exothermic processes state functions Enthalpy Enthalpies of Reaction. Calorimetry heat capacity and specific heat constantpressure calorimetry
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Chapter 5:
Thermochemistry
Energy
Systems & Surroundings
Closed System
energy(as heat or work)
2H2(g) + O2(g)
¯
2H2O(l)+ energy
(system)
no exchg of matterwith surroundings
First Law of Thermo.
+q +w
 q  w
surroundings
surroundings
system
system
heat
heat
work
work
Endothermic
Exothermic
State Function
Enthalpy
system
DH > 0
surroundings
system
surroundings
DH < 0
Enthalpies of Reaction
DH = Hfinal  Hinitial
H2O(g)
241.8 kJ
44 kJ

+
Enthalpy
H2O(l)
285.8 kJ
Practice Ex. 5.2:
Calorimetry
heat capacity
specific heat
remember: this is change in temp.
Practice Ex. 5.3:
ConstantPressure Calorimetry
must be opposite in sign
if DT is positive then qrxn is exothermic
Practice Ex. 5.4:
insulating cup
rxn
q
soln
Bomb Calorimetry (ConstantVolume)
heat capacity of calorimeter
because rxn is exothermic
thermometer
insulation
water
rxn
Practice Ex. 5.5:
Hess’s Law
2H2O(g)® 2H2O(l)D H =  88 kJ
Practice Ex. 5.6:
Cgraphite® CdiamondD H = + 1.9 kJ
Enthalpies of Formation
Practice Ex. 5.9: