Problem Set

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Problem Set

• Chemical Reactions

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Polymerization
Metal surface
Initiation step
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Polymerization
Metal surface
Propagation steps
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Polymerization
Metal surface
Propagation steps
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Polymerization
Metal surface
Propagation steps
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Polymerization
Metal surface
Propagation steps
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Polymerization
Metal surface
Termination step
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Polymerization of Ethylene
C
M M M M M M M M M
CH3 - M

n H2C CH2
CH3 - H2C - CH2 n- M
polyethylene
ethylene monomer
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ThermochemistryFirst Law of Thermodynamics

• Edward A. Mottel
• Department of Chemistry
• Rose-Hulman Institute of Technology

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Chemical Thermodynamics

• Reading assignment
• Chang Chapter 6.1-6.3
• A study of the energy changes which accompany the
  physical and chemical changes of matter.
• Balanced chemical equations are used to describe
  changes in both physical state and molecular
  structure.

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A Thermodynamic Term
The total heat energy content (H) of a molecule.
Enthalpy
If a chemical process requires heat, the enthalpy
change (?H) is endothermic.
If a chemical process releases heat, the enthalpy
change is exothermic.
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Chemical Reactions

• Requires knowledge of the chemical nature of the
  reactants and products.
• Formula, phase, solubility, ionic character.
• Equations corresponding to these processes should
  be balanced and completely annotated (g, l, s,
  aq).

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Solution ReactionsEndothermic and Exothermic
NH4(aq) NO3(aq)
DHsoln 25.8 kJ?mol1
2 H(aq) SO42(aq)
DHsoln -96.2 kJ?mol1
exothermic
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Changes in Physical StateReactions should be
balanced and annotated
Enthalpy of vaporization of water
Enthalpy of sublimation of water
Enthalpy of fusion of water
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Chemical ReactionsExamples
Decomposition
Single replacement
Double replacement
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Chemical ReactionsCombustion and Formation
Combustion
Formation
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Write the equation for each of the following
processes
Combustion of sucrose (C12H22O11)
Formation of sucrose
more examples
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Combustion and Formation Write the equation for
each of the following processes
Combustion of iron(II) sulfide to form sulfur
dioxide
Formation of nickel(II) nitrate
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Thermodynamic Terms

• Heat, q.
• Work, w.
• Internal energy, E or U
• System
• Surroundings
• Enthalpy, H
• State Functions

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Thermal Energy
Heat flows form a warmer body to a cooler body.
q
What is the difference between heat and
temperature?
Are heat and temperature intensive or extensive
properties?
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Thermal Energy
Heat flows form a warmer body to a cooler body.
Intensive properties are independent of amount.
Are heat and temperature intensive or extensive
properties?
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Work
Work has an intensive and a capacitive factor.
What is the difference between work and being
tired?
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Work
Type of Work
Intensity
Capacity
mechanical
force
distance
expansion
pressure
volume change (dV)
electrical
gravitational
gravity
height x mass
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Internal Energy

• E or U
• The total kinetic and potential energy of a
  molecule or ion
• Molecular motion
• Electronic changes

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Molecules Store Energy inMolecular Motion
rotation
vibration
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Electronic Changes
endothermic change in electron energy levels
exothermic bond formation
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First Law of Thermodynamics
The change in internal energy of a system
is equal to the energy added to the system, minus
the energy lost by the system.
DE energygained - energylost
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First Law of Thermodynamics
DE q w
Whats happening to the gas in the rigid bulb?
The change in internal energy is equal to the
heat added and the work done on the system.
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System - any region of space or material which is
considered in dealing with energy changes that
matter undergoes.
Closed system
Isolated system
Surroundings - Everything else (the rest of the
universe).
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First Law of Thermodynamics
DE q w
Whats happening to the temperature of the gas?
Why?
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First Law of Thermodynamics
DE q w
Explain what is happening using the First Law of
Thermodynamics.
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Internal Energy
The total energy (E or U) of a molecule or ion is
due to all sources of kinetic and potential
energy.
translation
rotation
vibration
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Molecules Store Energy inMolecular Motion
rotation
vibration