How to use these slides

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How to use these slides
Prof. Philipse uses these slides in his Physical
Chemistry lectures in the course Energie en
Materie. They summarize important concepts from
the material in Ball to be studied for the
exam. The slides do not replace these lectures.
It would be a good idea to supplement the slides
with your own lecture notes. Some topics from
Ball are skipped in the lectures, and some
(do-it-yourself)slides are not projected. These
topics and slides should not be missed and you
are urged to study them. For further explanation,
if needed, ask Prof. Philipse or your tutorial
(werkcollge) assistant. Consult the study
guide (studiehandleiding) for further
information on program and exam.
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Energy Matter
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• A. Philipse
• Kruyt N706
• A.P.Philipse_at_chem.uu.nl

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Van t Hoff Laboratory for Physical and Colloid
Chemistry University Utrecht
7 nov. 2007
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Energy Matter Physical Chemistry Part
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4
Energy Matter Inorganic Chemistry Part
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5
D.W. Ball Physical Chemistry
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6
The Two Main Themes
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• Matter in Equilibrium
• Spontaneous direction (of chemical reactions)
  towards equilibrium.
• What energy has to do with it.
• Matter in Motion
• Rates of reactions and molecules.
• What energy has to do with it.

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Lecture 1
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• Motivation
• Can we predict spontaneous direction of
  reactions?
• First formulation of First Second Law energy
  entropy
• The First Law
• Conversions of energy
• Energy is conserved
• Thermodynamic system
• Energy exchange work and heat
• First Law for isolated systems

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2 Mg O2 ? 2 MgO
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1
2
3
Time
4
5
6
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2 MgO ? 2 Mg O2 why not?
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1
2
3
Time
4
5
6
10
Na ½ Cl2 ? NaCl-
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One electron changes a very reactive metal and a
poisonous gas to table salt
Cl2
Electron
NaCl
Na
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Reverse reaction does not occur spontaneously
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Hydrogen oxidation
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• Reverse reaction does not occur spontaneously.
• Possibility and spontaneity of reaction
  determined by

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Energy U

Entropy S
First Law
Second Law
of thermodynamics

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The First Second Law of Thermodynamics
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System
13
Less obvious case glycine oxidation
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• 2 NH2CH2COOH 3 O2 ? H2NCONH2 3 CO2 3 H2O

Glycine
Ureum
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How to
- predict the spontaneous direction. - calculate
equilibrium constant.
Glycine
Ureum
concentrations at equilibrium
Ureumeq Glycineeq
K
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From the First and Second Law of Thermodynamics
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First Law is about the amount of energy
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• The total energy U is constant
• ?Utot Utot - Utot 0

after reaction
before
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Second Law is about distribution of energy
The total entropy S cannot decrease ?Stot
Stot - Stot 0
after reaction
before
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The First Law Energy is Conserved
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Energy conversion
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reflection
radiation
Sun
Earth
PHOTOSYNTHESIS (1 solar energy)
NUCLEAR FUSION
absorption
CHEMICAL ENERGY

• Starch
• Glucose
• Coal etc.

FOOD
FUEL
WORK
Kinetic Energy
HEAT ( disordered molecular motion)
17
First Law of Thermodynamics
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Energy U can only be stored, transported or
converted
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Storage battery, chemical bond
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Transport electricity, light, heat q, work w
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Conversion potential to kinetic
energy chemical reactions etc.
18
Thermodynamic system is a small part of the
universe
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• Three different boundaries between system
  surrounding

surroundings
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Exchange of
energy matter
energy X
X X
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Two types of energy exchange between system
surroundings
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work w
heat q
w collective transport by molecules q
energy transport by disordered molecular motions
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q
w
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First Law for isolated systems
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surroundings
Zn 2H Zn2 H2
system
heat q
work w
isolating boundary
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• Internal Energy Usys sum of all energies in
  system
• First Law ?Usys 0 isolated system

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Lecture 2
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• Gases
• Pressure and mechanical equilibrium
• Temperature and thermal equilibrium
• Moles Avogadros number
• State of a gas state variables
• Equation of state
• Ideal Gas
• Ideal gas law
• Ideal behaviour
• Molar volume Avogadros principle
• Gas mixtures Daltons law
• Isotherms, isochors and isobars

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Example of closed thermodynamic system
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Pressure P Volume V Moles n Temperature
T
First Law ?U q w
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Pressure P is due to bouncing molecules
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colliding molecules exert force on wall
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Spontaneous motion towards mechanical Equilibrium
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25
Temperature T measures molecular Kinetic Energy
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A
B


TA gt TB
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Ekin ½ mv2 m molecular mass
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Average Ekin 3/2 kT k Boltzmann constant
26
Spontaneous heat transfer towards thermal
equilibrium
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27
Example of closed thermodynamic system
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Pressure P Volume V Temperature T
Moles n
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First Law ?U q w
28
Molecules counted in moles, just as apples in
dozens
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29
Number of moles, n
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Nav Avogadros number 6.022 1023 mol-1
number of atoms in exact 12 g 12C number of
particles in 1 mole
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Moles of what?
anything that can be counted!
30
Concepts of thermodynamics are (relatively) easy
to understand for gases
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Pressure P Volume V Moles n Temperature T
Equilibrium State State variables
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31
State of a gas is independent of its history
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state 1
state 2
P1, V1
P2, V2
State variables
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32
State variables only differences count
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That is why differentials are an essential part
of Thermodynamics
H1 1000 meter
?H -990 m for any path
H2 10 meter
H 0
H2
?H ? dH H2 H1
H1
33
Differentials and Integrals not only in math
course the are really out there.....
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34
Equation of State connects state variables
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P, V, n and T are NOT independent
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P P( n, V, T) equation of state
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For ideal gas PV nRT R gas constant
k x Nav
Boltzmann constant
Avogadros number
35
Ideal Gas Law does not discriminate molecules
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State Pressure P Volume V
Moles n Temperature T
velocity v
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Equation of state
PV nRT
for ideal gas
mass m
36
Molar volume of an ideal gas
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P
P
PV nRT
molar volume
RT P
H2
H2O
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Non-ideal gas
constant for fixed P, T (Avogadros principle)
37
Molar volume is generally not constant
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One mole of

38
Do-it-your-self slides
Make sure you understand the following three
slides (39-41) related to the ideal gas law. Why
is work not a state variable (slide 42)?
39
Ideal molecules are non-interacting molecules
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• No (effect of) molecular interactions
• Low pressure

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PV nRT
40
PV nRT the P-V-T diagram
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Isotherm PV nRT T constant Isochore V
constant Isobar P constant
isochore
41
Gas mixtures Daltons Law
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Partial pressure Pi of component i

xi mole fraction component i
42
Work is NOT a state variable, but path dependent
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H1
H1
B
A
H2
H2
A
B
work ? work