Chem. 412 – Phys. Chem. I. Spontaneous Processes Mixing of gases Heat flow from hot to cold (Most)...
26
Chem. 412 – Phys. Chem. I T e m p era tu re P h a se T ran sitio n s H e a t E n g in es Z e ro E n tro p y fo r P e rfe c t C ry sta ls D o w n to Z e ro K 3 rd L a w E ntro p ies 3 rd L a w o f T herm odynam ics E n tro p y o f th e U n ive rse C a rn o t C ycles H e a t P um ps S u p e rc o o le d C alcu latio n s R e ve rsib le vs . Irre ve rsib le V olum e P re s su re E n tro p y Changes 2 n d L a w o f T herm odynam ics E n tro p y/D iso rd er D isb u rs e m e n t o f E nergy E n tro p y - 2 n d & 3 rd L a w s o f T herm odynam ics
-
Upload
jonah-ramsey -
Category
Documents
-
view
216 -
download
0
Transcript of Chem. 412 – Phys. Chem. I. Spontaneous Processes Mixing of gases Heat flow from hot to cold (Most)...
Chem. 412 – Phys. Chem. IChem. 412 – Phys. Chem. I
Tem perature
Phase T ransitions
Heat Engines
Zero Entropy for Perfect CrystalsDow n to Zero K3rd Law Entropies
3rd Law of Therm odynam ics
Entropy of the Universe
Carnot Cycles Heat Pum ps
Supercooled Calculations Reversible vs. Irreversible
Volum e Pressure
Entropy Changes
2nd Law of Therm odynam icsEntropy/Disorder
Disbursem ent of Energy
Entropy - 2nd & 3rd Law s of Therm odynam ics
Spontaneous ProcessesSpontaneous Processes
• Mixing of gases• Heat flow from hot to cold• (Most) macroscopic events are irreversible
Key Sign of Spontaneity: Look for direction of change that leads to a chaotic dispersal of total energy.
Key Sign of Spontaneity: Look for direction of change that leads to a chaotic dispersal of total energy.
The Spontaneous Expansion of a Gas
• Why does the gas expand?
Entropy and the Entropy and the Second Law of Second Law of
ThermodynamicsThermodynamics
Second Law of ThermodynamicsSecond Law of Thermodynamics
T
qdS rev
dPVdSTdH
dVPdSTdU
:(2)Equation Master
:(1)Equation Master
ΔS Variations in terms of V & T ChangesΔS Variations in terms of V & T Changes
V
dVnR
T
dTCS V
ΔS Variations in terms of P & T ChangesΔS Variations in terms of P & T Changes
P
dPnR
T
dTCS P
V
dVnR
T
dTCS V
dVPdSTdU :(1)Equation Master
dPVdSTdH :(2)Equation Master
P
dPnR
T
dTCS P
ΔS Variations @ Constant VolumeΔS Variations @ Constant Volume
T
dTCS V
ΔS Variations @ Constant TemperatureΔS Variations @ Constant Temperature
P
dPnR
V
dVnRS
V
dVnR
T
dTCS V
P
dPnR
T
dTCS P
ΔS Comparisons: V versus TΔS Comparisons: V versus T
Double T at constant VDouble T at constant VDouble V at constant TDouble V at constant T
T
dTCS V
V
dVnRS
ΔS Variations @ Constant PressureΔS Variations @ Constant Pressure
ephase/stat sameover T
dTCS P
(pt) ns transitiophaseat pt
ptpt T
HS
P
dPnR
T
dTCS P
T
qdS rev
ENTROPY OF THE UNIVERSEENTROPY OF THE UNIVERSE
Die Enegie der Welt ist Konstant;Die Enegie der Welt ist Konstant;
die entropie der Welt einendie entropie der Welt einen
Maximum ZuMaximum Zu
Entropy is the Arrow of TimeEntropy is the Arrow of Time
A Brief History of Time S. Hawking’s Grand Design: The Meaning of Life (19 min)
Spontaneous Mixing of GasesSpontaneous Mixing of Gases
• Driving force due to Entropy• Compare Interdiffusion of gases to playing
“Bridge” (Cards): Chance of getting 13 cards of same suit (after proper shuffles) is <<<<<<<< Chance of getting some mixture of cards.
• S = -k pi ln pi (via Statistical TD)
cardsforx
ob 521035.6
1.Pr
11
3rd Law of Thermodynamics3rd Law of Thermodynamics So = 0 for any physical or chemical change involving perfect crystals at absolute zero.
• 3rd Law Entropies:
• For Irreversible Processes:
)(lnTdCT
dTCS
PP
0 surro
syso
univo SSS
Supercool ExampleSupercool ExampleAt constant pressure of 1 atm, calculate ΔSsys , ΔSsurr and ΔSuniv upon the sudden freezing of 1 mole of H2O at -10.00°C. (sudden freezing of supercooled water)
Given: CP(ℓ) = 75.3 J K-1 mol-1
CP(s) = 36.9 J K-1 mol-1
ΔHf° = 5950. J mol-1 (s → ℓ)
Sketch a Hess’ Law diagram replacing the irreversible process with three reversible steps.
Calculate ΔSsys [ ΔS(H2O) ]
Calculate ΔSsurr [ Need to find ΔHsurr at 263.15 K ]
Calculate ΔSuniv
Supercool Example: ΔSsysSupercool Example: ΔSsys
Supercool Example: ΔSsurrSupercool Example: ΔSsurr
2 :where
)(2
1
2
1
TcTbaC
dTCHd
P
T
T P
T
T rxn
Temperature Dependence of CP and Hrxn: ΔHsurr & ΔSsurrTemperature Dependence of CP and Hrxn: ΔHsurr & ΔSsurr
2 :where
)(2
1
2
1
TcTbaC
dTCHd
P
T
T P
T
T rxn
Supercool Example: ΔSunivSupercool Example: ΔSuniv
Supercool Example: ΔSsysSupercool Example: ΔSsys
F12
Temperature Dependence of CP and Hrxn: ΔHsurr & ΔSsurrTemperature Dependence of CP and Hrxn: ΔHsurr & ΔSsurr
2 :where
)(2
1
2
1
TcTbaC
dTCHd
P
T
T P
T
T rxn
F12
Supercool Example: ΔSsurrSupercool Example: ΔSsurr
F12
Heat EnginesHeat Engines
T2
T1
Heat Source
Heat Sink
q2
-q1
work-w 2
q
w
2q
w
= efficiency = efficiency
Web AnimationImages
YT-video(rubber band)
Heat PumpsHeat Pumps
T1
T2 High T
q1
-q2
workw
1q
w
1q
w
Low T
Net Results of a Carnot CycleNet Results of a Carnot Cycle
0
ln
ln
ln)(
1
2
11
1
2
22
1
2
12
S
V
VRTq
V
VRTq
V
VTTRw
2
12
T
TT
EngineHeat
2
12
T
TT
EngineHeat
1
12
T
TT
PumpHeat
1
12
T
TT
PumpHeat
Perpetual Motion Machine of the Second KindPerpetual Motion Machine of the Second Kind
Hot Reservoir T2
Cold Reservoir T1
q2
-q1
-w
-q2’
q1’
Heat Pump Engine
Web-link machines
Ng-Poli-Machine
Perpetual Motion Kilty
cartoon
Tem perature
Phase T ransitions
Heat Engines
Zero Entropy for Perfect CrystalsDow n to Zero K3rd Law Entropies
3rd Law of Therm odynam ics
Entropy of the Universe
Carnot Cycles Heat Pum ps
Supercooled Calculations Reversible vs. Irreversible
Volum e Pressure
Entropy Changes
2nd Law of Therm odynam icsEntropy/Disorder
Disbursem ent of Energy
Entropy - 2nd & 3rd Law s of Therm odynam ics
T
qdS rev
dPVdSTdH
dVPdSTdU
:(2) ME
:(1) ME V
dVnR
T
dTC
P
dPnR
T
dTCS VP
pt
ptpt T
HS
0 surr
osyso
univo SSS
