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AP CHEMISTRY CHAPTER 19: CHEMICAL THERMODYNAMICS (Pgs. 812-843)
EQ: _______________________________________________________________________________________________
Questions:
SECTION 1-First Law of Thermodynamics-2
• You will recall from Chapter 5 that
energy cannot be _____________ or
________________.
• Therefore, the total energy of the
universe is a __________________.
• Energy can, however, be ___________
from one form to another or
_______________ from a system to the
____________ or vice versa.
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Spontaneous Processesz-4
_____________________ proceed
without any outside assistance.
The gas in vessel A will spontaneously
effuse into vessel B, but it will not
_________________ return to vessel A.
Processes that are spontaneous in one
direction are _______________ in the
_________________direction.
Enthalpy/Entropy-3
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Experimental Factors Affect Spontaneous
Processes-5
• ____________and ___________ can
affect spontaneity.
• An example of how temperature affects
spontaneity is ice _____________ or
_____________.
Reversible and Irreversible Processes-6
• Reversible process:
SECTION 2-Entropy-7
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_____________ can be thought of as a
measure of the randomness of a system.
It is a state function:
Irreversible processes:
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_____________ is the heat absorbed by
a system during a _________________
process.
_______________ is a measure of the
________________ in a system.
Both play a role in determining whether
a process is _____________________.
It can be found by heat transfer from
surroundings at a given temperature:
Second Law of Thermodynamics-8
The entropy of the universe ____________ in any _______________ processes.
This results in the following relationships:
Questions:
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SECTION 3-Entropy on the Molecular Scale-9
________________ described entropy on the molecular level.
Gas molecule expansion: Two molecules are in the apparatus above; both start in one side.
What is the likelihood they both will end up there? (1/2)2
If one mole is used? (1/2)6.02×1023! (No chance!)
Gases _______________ expand to fill the volume given.
Most probable arrangement of molecules: approximately ____________molecules in each
side
Statistical Thermodynamics-10
Thermodynamics looks at _______
properties of substances (the big
picture).
We have seen what happens on the
molecular scale. How do they relate?
We use statistics (probability) to relate
them. The field is called ____________
______________
_____________: A single possible
arrangement of position and kinetic
energy of molecules
Entropy Change-12
Since entropy is a state function, the
___________ value minus the
__________value will give the overall
change.
In this case, an _____________ in the
number of microstates results in a
______________ entropy change
(__________ disorder).
Eq:
Molecular Motions-14
Molecules exhibit several types of motion.
 Translational:
Boltzmann’s Use of Microstates-11
Because there are so many possible
microstates, we can’t look at every
picture.
• _____ represents the ________ of
microstates.
• Entropy is a measure of:
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Effect of Volume and Temperature Change on
the System-13
• If we ___________ volume, there are
___________ positions possible for the
molecules. This results in _________
microstates, so _____________ entropy.
• If we ______________temperature, the
average kinetic energy ____________.
This results in a greater distribution of
molecular speeds. Therefore, there are
__________ possible kinetic energy
values, resulting in more microstates,
__________________ entropy.
Entropy on the Molecular Scale-15
The number of microstates and, therefore, the
entropy tend to increase with increases in

 Vibrational:
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 Rotational:
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Note: More atoms means ________
microstates (more possible molecular
________________).
The connection between the number of
microstates and the entropy of the
system is:
Questions:
Entropy and Physical States-16
Entropy increases with the freedom of
motion of molecules.
S(g) ____S(l) _____S(s)
Entropy of a system ______________
for processes where
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Third Law of Thermodynamics-17
The entropy of a pure crystalline
substance at absolute zero is ____.
Consider all atoms or molecules in the
perfect lattice at 0 K; there will only be
___________ microstate.
Eq:
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SECTION 4-Standard Entropies-18
The reference for entropy is ______,
so the values for elements are not
_______________________
Standard molar enthalpy for gases are
generally ___________ than liquids and
solids. (Be careful of size!)
Standard entropies _____________ with
_________________.
Standard entropies increase with
number of ___________ in a formula.
Entropy Changes in Surroundings-20
•
Entropy Changes-19
Entropy changes for a reaction can be
calculated in a manner analogous to
that by which H is calculated:
where n and m are the ________________ in
the balanced chemical equation.
Entropy Change in the Universe-21
The universe is composed of the
______________ and the
__________________.
• Therefore,
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Heat that flows into or out of the system
changes the ___________ of the
__________________.
For an isothermal process:
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For spontaneous processes
At constant pressure, qsys is simply H°
for the system:
Section 5-Total Entropy and Spontaneity-22
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• Substitute for the entropy of the
surroundings:
Gibbs Free Energy-23
1.
2.
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Multiply by −T:
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Rearrange:
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Call −TΔSuniverse the ________________:
3.
Questions:
Standard Free Energy Changes-24
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Analogous to standard enthalpies of
formation are standard free energies of
formation, Gf°:
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where n and m are the stoichiometric
coefficients.
SECTION 7-Free Energy and Equilibrium-26
• Under any conditions, standard or
nonstandard, the free energy change
can be found this way:
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SECTION 6-Free Energy Changes-25
How does ΔG change with temperature?
Since reactions are spontaneous if
____________, the sign of enthalpy and
entropy and the magnitude of the
temperature matters to spontaneity.
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Free Energy and Equilibrium-27
At equilibrium, Q = _____, and G = ___.
The equation becomes:
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Rearranging, this becomes
(Under standard conditions,
concentrations are ___ M, so Q = ___
and ln Q = ____; the last term drops
out.)
SUMMARY
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