chemistry 163b lecture 25- concluding factoids …...2 chemistry 163b lecture 25- concluding...
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Chemistry 163BLecture 25- Concluding Factoids W2013
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Chemistry 163B
Concluding Factoids
and
Comments
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neuron, resting potential
http://projects.gw.utwente.nl/pi/sim/Bovt/concep4.gif
http://www.uta.edu/biology/westmoreland/classnotes/1442/Chapter_48_files/image009.jpg
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Chemistry 163BLecture 25- Concluding Factoids W2013
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resting potential and Nernst Equaiton
ln
0
[ ]
[ ]
[ ]ln .02569ln
[ ]
140.02569ln 0.086
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F
F
inside
outside
inside
outside
RTQ
n
KQ
K
KRTQ
n K
mMV
mM
major source of potential: [K+]outside(Cout) [K+]inside(Cin)
The computed number is a little higher than the quantity measuredin experiments (-70 mV) but all the factors in this complex physical process
have been accounted for. http://www.medicalcomputing.net/action_potentials.html
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Gibbs-Duhem
the partial molar quantities do not vary independently
vocabulary
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Chemistry 163BLecture 25- Concluding Factoids W2013
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Gibbs-Duhem
2
2
2 2, , , ,H O H O
H OEtOHEtOH H O
EtOH EtOHT P n T P n
VVX X
n n
http://www.chem.unt.edu/faculty/cooke/3510/3510_chap7.ppt
what are
, , , ,b b
a b
a aT P n T P n
V Vand
n n
when a and bform an ideal solution ?
do idealsolutionsobey the
Gibbs-Duhemrelation?
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non-ideal solutions
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Chemistry 163BLecture 25- Concluding Factoids W2013
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benzene-toluene, quite ideal (similar to Fig 9.2 E&R) !!
http://www.chem.ucsb.edu/coursepages/06fall/1C-Watts/dl/Lecture_Notes/Lecture16.%2011-8-06Colligative%20Properties%20Solutions.pdf
( ) ( )
( )
A A A B B B
total A A B B
P X P P X P
P X P P P
Raoult's Law of Ideal Solutions
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ideal solution: T vs X (P=1 atm) for solution-vapor equilibrium
toluene (b.p.=383.78) + benzene (b.p.=353.25)
tol+ben (solution)
[fremaining=2]
tol+ben (vapor)
[fremaining=2]
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Chemistry 163BLecture 25- Concluding Factoids W2013
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non-ideal solutions: azeotrope
Definition[s]:
• constant boiling liquid
• solution where the mole fraction of each component is the same in the liquid (solution) as the vapor
• boiling point of azeotrope may be higher or lower than of pure liquids
( ) ( )vi iX X
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non-ideal solutions: positive deviations from ideal solution (E&R pp 214-218)
• positive deviations from Raoult’s Law:smaller forces betweencomponents than ‘within’ components
• total pressure greater than ideal solution
CS2 () + (CH3)2CO ()
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Chemistry 163BLecture 25- Concluding Factoids W2013
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acetone-carbon disulfide: positive deviation low boiling azeotrope
http://www.separationprocesses.com/Distillation/Fig011b.htm
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low boiling azeotrope
• weaker between component forces (AB) (than A A, B B)
• fractional distillation leads to constant boiling azeotrope in vapor
• and (in pot after azeotrope boils off)• (XA)initial > (XA)azeotrope pure A • (XA)initial < (XA)azeotrope pure B
http://www.solvent--recycling.com/azeotrope_1.html
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Chemistry 163BLecture 25- Concluding Factoids W2013
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Water-Ethanol Mixture
For the water-ethanol mixture, the azeotropeconcentration corresponds to ~95% of ethanolin the mixture. This is the limit that can bereached by distillation of a less-alcohol-richmixture.
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non-ideal solutions : negative deviations from ideal solution
• negative deviations from Raoult’s Law: greater forcesbetween components than ‘within’ components
• total pressure lower than ideal solution
CHCl3 () + (CH3)2CO ()
http://dwb4.unl.edu/Chem/CHEM869W/CHEM869WImages/raoult2.gif
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Chemistry 163BLecture 25- Concluding Factoids W2013
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acetone-chloroform: negative deviation high boiling azeotrope
http://www.chm.bris.ac.uk/~chdms/Teaching/Chemical_Interactions/images/pic192.jpg
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high boiling azeotrope
• stronger between component forces (AB) (than A A, B B)
• fractional distillation leads to pure component in vapor until solution (pot) reaches azeotrope composition
• (XA)initial > (XA)azeotrope pure A • (XA)initial < (XA)azeotrope pure B
http://www.solvent--recycling.com/azeotrope_1.html
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Chemistry 163BLecture 25- Concluding Factoids W2013
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simple distillation
http://www.docbrown.info/page12/gifs/distill.gif
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simple distillation (one evaporation; Tbp varies as X changes)
( )vbenzeneX
( )solutionbenzeneX
X
increases gradually
( )solutionbenzene
bp
add heat
decreases
T
benzeneX
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Chemistry 163BLecture 25- Concluding Factoids W2013
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fractional distillation
http://www.wpbschoolhouse.btinternet.co.uk/page12/gifs/FracDistRed.gif
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Fractional Distilation
liquid composition
vapor composition
I. start with 50-50 mixture
Tbp 366
II. vapor Xvbenzene .72
III. condense Xbenzene .72
Tbp359.5
IV. evaporate
vapor Xvbenzene .88
V. etc, ...
VI. apporachesXbenzene=1
I
II
III
IV
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Chemistry 163BLecture 25- Concluding Factoids W2013
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T vs progress for a distillation
http://www.uwlax.edu/faculty/koster/Image119.gif
(top of column)
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Electrolytes andDebye-Huckel Theory
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Chemistry 163BLecture 25- Concluding Factoids W2013
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activity coefficients for ions (HW8 #58)
2
2
2
2 2
22
2
( ) ( )
( )
( )
2
( )
( )
( ) ( ) 2 ( )
1
Ba aq Cl aq
sp
BaCl s
BaCl s
Ba aq Ba
Cl aq Cl
BaCl s Ba aq Cl aq
a aK
a
a
a Ba
a Cl
determine and independently
but only
2
2
Ba Cl
Ba Cl
cannot
223
23 2
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1 (1)sp
sp
MMBa ClK
K Ba Cl
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Debye-Hückel Theory
• ‘a priori’ calculation of activity coefficients, ±, for ions
• expect ± < 1 since ions not independent [effective
concentration reduced; a± < c± ]
• is calculated as work done to bring other charges to
region surrounding ion in question
• the result is
3 1
2 2
2
ln
where depends on the solvent's dieelectric constant and other physical constants
are the (interger) charges on the cation and anion
1and I= is the ionic strength of
2 i ii
z z T I
z and z
m z
i the solution, m is molal concentration of
[ & : Eqn 10.32 with from Eqn. 10.29]
ion
E R
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Chemistry 163BLecture 25- Concluding Factoids W2013
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Debye-Hückel Theory
1
2
1
2
2 2
log 0.5092 for water solvent at 298.15K
ln 1.173 (E&R eqn 10.33)
1I= ionic strength
2
i i i ii
z z I
z z I
m z m z
3 1
2 2
2
ln
where depends on the solvent's dieelectric constant and other physical constants
are the (interger) charges on the cation and anion
1and I= is the ionic strength of
2 i ii
z z T I
z and z
m z
i the solution, m is molal concentration of
[ & : Eqn 10.32 with from Eqn. 10.29]
ion
E R
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observations: thermo heat
• Count Rumford, 1799 • observed water turning into steam when canon barrel was bored• work heat
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Chemistry 163BLecture 25- Concluding Factoids W2013
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1st law
0
other
other
dU dq PdV dw
dU
dH dq VdP dw
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observations: mechanical efficiency of steam engine
• Sadi Carnot, 1824 • efficiency of engines
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Chemistry 163BLecture 25- Concluding Factoids W2013
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2nd Law
1
0
0
Lfficiency
H
rev
UNIVERSE
other
other
T
T
dqdS
Tdq
dST
S
dS
dU TdS PdV dw
dH TdS VdP dw
microstates and disorder
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“Applications”
How does knowledge about efficiencies of steam engines, mechanical systems, etc, relate to processes in chemical, biological, and geological systems?
ANSWERED BY:
J. W. Gibbs- arguably the frist great American scientist who combined the concepts of heat and entropy and proposed “[Gibbs] Free Energy”, G, a thermodynamic state function that leads to a whole spectrum of applications
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Chemistry 163BLecture 25- Concluding Factoids W2013
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Free Energy and Equilibrium
, , ,
, ,,
T P T P T P
T P T PT P
other
other
systemsurroundings
SS
G H T S
G HS
T T
dG SdT VdP dw
dA SdT PdV dw
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Applications
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Chemistry 163BLecture 25- Concluding Factoids W2013
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quantitative-deductive mathematical abilities
2
2
/
/
P
reac reac
P
T H
T T
T H
T T
2
lnreac
oeq
P
HK
T RT
, , j i
ii i T P n n
HdH TdS VdP dn
n
, ,all allP n S n
V T
S P
Maxwell-Euler
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Final Exam
• Conceptual and ‘analytical math’ from throughout term
• Problems concentrate on material since last exam
•Ideal Solutions and corrections for non-ideality
• Phase equilibria and phase diagrams
one-component, relationship of T and P for one component equilibrium
two-component (solid V solution and solution V vapor )
• Colligative properties (HW8)
• Electrochemistry (HW8)
• Φ and ΔG, Δm
• Three cells
• Vocabulary from concluding factoids
• BRAIN POWER
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Chemistry 163BLecture 25- Concluding Factoids W2013
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FINIS(except)