chapter 10 solution lecture solution ecture notes
TRANSCRIPT
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Chapter 10
Properties of Solutions
17.1 Solution Composition
17.2 The Thermodynamics of Solution Formation (skip)
17. Factors !ffectin" Solu#ility
17.$ The %apor Pressures of Solutions
17.& 'oilin"Point le*ation and Free+in"Point ,epression
17.- smotic Pressure
17.7 Colli"ati*e Properties of lectrolyte Solutions
17./ Colloids GAS
SOLID LIQUID
Freezing
Melting
S u b l
i m a t i o
n
D e p
o s i t i o
n
C o n d e n s a t
i o n
E v a p o r a t i o n
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Colli"ati*e Properties of Solutions
For Colligative properties the difference
#eteen a pure sol*ent and dilute solutiondepends only on the number of solute
particles present and not on their
chemical identity.
3amples
4 Vapor Pressure Depression
4 Boiling Point Elevation
4 Melting Point Depression 4 Osmotic Pressure
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Lowering of Vapor Pressure
4 %apor Pressure of a sol*ent a#o*e a dilute solutionis alays less than the *apor pressure a#o*e the
pure sol*ent.
Elevation of Boiling Point
4 The #oilin" point of a solution of a non*olatilesolute in a *olatile sol*ent alays e3ceeds the
#oilin" point of a pure sol*entBoiling
• liuid in euilibrium "it# its vapor at t#e e$ternal pressure%
Boiling Point
• &apor press ' e$ternal pressure
Normal boiling point
• Vap press. = 1 atm
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Phase diagrams for pure water red
lines!
and for an a"ueous solution
containing a nonvolatile
solution #lue lines!.
Elevation of BoilingPoint $ VaporPressure Depression
∆T = K bm
solute
∆T is the boiling point elevation
K b is molal boiling - point elevation constant
msolute
is the molality of the solute in solution
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Solution Composition
Solution( A #omogeneous mi$ture )mi$ed at level o* atoms
mole+ules or ionsSolvent(
Solute(
,#e ma-or +omponent
,#e minor +omponent
,#e solute and solvent +an be an.
+ombination o* solid ) s/0 liuid )l /0 and
gaseous ) g / p#ases%
Dissolution( ,"o )or more/ substan+es mi$ at t#e level o*
individual atoms0 mole+ules0 or ions%
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Solution Composition
Mass percentage (weight percentage):
mass percentage of the component =
X 100mass of component
total mass of mi!t"re
Mole fraction: ,#e amount o* a given +omponent )in moles/
divided b. t#e total amount )in moles/
12 ' n2#)n2 3 n4/ *or a t"o +omponent s.stem
14 ' n4#)n2 3 n4/ ' 2 $ 12 or 12314'2
Mass %raction& Mole %raction& Molalit' an
Molarit'
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Molalit'msolute '
moles solute per 5ilogram solvent
' moles per 5g or )mol 5g62/
Molarit' (biochemists pa' attention)
csolute '
moles solute per volume solution
' moles per liter of solution )mol L62/
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Factors !ffectin" Solu#ility
1. 5olecular 6nteractions
4 Review chapter 4 4 Polar molecules ater solu#le hydrophilic (ater
lo*in")
.". %itamins ' and C atersolu#le
4 8onpolar molecules solu#le in nonpolarmolecules hydropho#ic (ater fearin")
.". %itamins ! , 9 and fatsolu#le
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Factors !ffectin" Solu#ility of :ases
1. Structure ffects
2. Pressure ffects
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;enry
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:#en t#e partial pressure o* nitrogen over a sample o* "ater at
2;% atm0 t#e +on+entration o* nitrogen in t#e "ater is
?%@ $ 2>6B mol L62% Compute 8enr.9s la" +onstant *or nitrogen in
"ater at t#is temperature%Given
PN2
= 9.20 atm
cN2 = [N2] = 5.76x10−3
mol/LHenry's Law
PN2
= k N2 X N
2
X N2
= nN2
nN2
+ nH2O
≈nN2
nH2O
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)iter1ass"meNe!t
%in(
*i+en
X
P
,
rearrange
X, P
-
N
-N
-N
-N
-N
-N
=
=
:#en t#e partial pressure o* nitrogen over a sample o* "ater at
2;% atm0 t#en t#e +on+entration o* nitrogen in t#e
"ater is ?%@ $ 2>6B mol L62% Compute 8enr.9s la" +onstant *or
nitrogen in "ater at t#is temperature%
OO n
n
nn
n
X
X
-
-N
-
-N
-N
-N
-N
-N
-N
/--
N
-N
, P
)awsenr'
mol#l.23!1045Nc
atm6.-0P
*i+en
≈
=
=
=
=
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:#en t#e partial pressure o* nitrogen over a sample
o* "ater at 2;% atm0 t#en t#e
+on+entration o* nitrogen in t#e "ater is ?%@ $ 2>6B
mol L62% Compute 8enr.9s la" +onstant *or nitrogen
in "ater at t#is temperature%%in(
*i+en
X
P
,
-N
-
N
-N
atm2>$C%CA
2%>B@C$2>
atm;%4>
Find
Given
1
75
2>$2%>B@C
2CgDmol
2>>>gDl
molDl?%@A$2>
n
n1
<
<
4 E
4 E
4 E
<
B
O4
8
4 E
4 E
=
===
=
⎟⎟⎠
⎞⎜⎜⎝
⎛=≈
−
−
−
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Factors !ffectin" Solu#ility
1. Structure ffects
2. Pressure ffects
. Temperature ffects for !>ueous Solutions
The solu#ility of some
solids as a function oftemperature.
,#e aueous solubilities o* most solids
in+rease "it# in+reasing temperature0
some de+rease "it# temp%Endothermic % heat is a#sor#ed #y the
system thin& evaporation of water' or
melting of ice!
E(othermic % heat is evolved #y the systemthin& fire' or free)ing of water!.
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Factors !ffectin" Solu#ility
1. Structure ffects
2. Pressure ffects
. Temperature ffects for !>ueous Solutions
The solu#ility of some gases in
ater as a function of
temperature at a constant
pressure of 1 atm.
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,#e greatest gas solubilit. *or a gas insolution is predi+ted under "#at
+onditions
2/ lo" ,0 lo" 7
4/ lo" ,0 #ig# 7
B/ #ig# ,0 lo" 7
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,#e greatest gas solubilit. *or a gas insolution is predi+ted under "#at
+onditions
2/ lo" ,0 lo" 7
-) low 7& high P
B/ #ig# ,0 lo" 7
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8ccoring to enr's aw& the sol"bilit'of a gas in a li9"i
2/ depends on t#e polarit. o* t#e liuid
4/ depends on t#e liuids densit.
B/ remains t#e same at all temperatures
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A++ording to 8enr.s La"0 t#e solubilit. o* agas in a liuid
2/ depends on t#e polarit. o* t#e liuid
4/ depends on t#e liuids densit.
B/ remains t#e same at all temperatures
) increases as the gas press"re abo+e
the sol"tion increases
?/ de+reases as t#e gas pressure above t#e
solution in+reases
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*he Person Behind the +cience
,rancois-Marie aoult /012-/32/!
4ighlights 4 1//- ?aoult@s la the partial pressure
of a sol*ent *apor in e>uili#rium ith asolution is proportional to the ratio of thenum#er of sol*ent molecules to non
*olatile solute molecules. 4 allos molecular ei"hts to #edetermined and pro*ides thee3planation for free+in" point depression
and #oilin" point ele*ation.
Moments in a Life 4 ?aoult as a prominent mem#er of the
"roup hich created physical chemistryincludin" !rrhenius 8ernst *an t@;off
Planck.
Psoln 5 6solventP7solvent
,or ideal
solutions
http://scienceworld.wolfram.com/chemistry/RaoultsLaw.htmlhttp://scienceworld.wolfram.com/chemistry/FreezingPointDepression.htmlhttp://scienceworld.wolfram.com/chemistry/BoilingPointElevation.htmlhttp://scienceworld.wolfram.com/chemistry/BoilingPointElevation.htmlhttp://scienceworld.wolfram.com/chemistry/FreezingPointDepression.htmlhttp://scienceworld.wolfram.com/chemistry/RaoultsLaw.html
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?aoult
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?aoult
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%apor pressure for a solution of to *olatile li>uids.
Negati+e e+iation
' solute6solvent attra+tions H solvent6solvent attra+tions
Positi+e e+iation
' solute6solvent attra+tions solvent6solvent attra+tions
,or non-ideal +olutions
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boiling point : ∆T = K bm
solute
freezing point : ∆T = K
f
m
solute
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Osmotic Pressure
Fourth Colli"ati*e Property
6mportant for transport ofmolecules across cellmem#ranes calledsemipermea#le mem#ranes
Osmotic Pressure = Π
Π B M ?T
ΠV B n ?T
Molarit. )M/ ' molesL or n&
PV = n;7
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Osmotic Pressure
The normal flo of sol*ent into the solution
(osmosis) can #e pre*ented #y applyin" ane3ternal pressure to the solution.
smotic Pressure useful for
,eterminin" the Molar Mass ofprotein and other macromolecules
small concentrations cause
lar"e osmotic pressures
Can pre*ent transfer of all soluteparticles
,ialysis at the all of most
plant and animal cells
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Dialysis8 ?epresentation of the functionin"
of an artificial kidney
! cellophane (polymeric)
tu#e acts as the semi
permea#le mem#rane
Purifies #lood #yashin" impurities
(solutes) into the
dialy+in" solution.
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A dilute aueous solution o* a non6disso+iating +ompound
+ontains 2%2; g o* t#e +ompound per liter o* solution and
#as an osmoti+ pressure o* >%>4 atm at a temperature o*
B@=C% Compute t#e molar mass o* t#e +ompound%
Strategy
1) useΠ= MRT to find M (mol/L)
2) Recall that # of moles =mass
mwt
3) Rearrange mwt =g
mole=
gLmole
L
=1.19
M
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A dilute aueous solution o* a non6disso+iating
+ompound +ontains 2%2; g o* t#e +ompound per liter
o* solution and #as an osmoti+ pressure o* >%>4 atm
at a temperature o* B@=C% Compute t#e molar mass o*t#e +ompound
S olution
1) use Π= MRT or M = Π
RT
c = Π
RT=
0.0288 atm
(0.0820 L atm mol−1K−1)(37 + 273.15K)
M = 1.132x10−3 mol/L
2) Rearrange M =g
mole=
gL
moleL
M =1.19
gL
1.132x10−3 mol/L= 1.05x103g/mol
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*he Person Behind the +cience
9.4. van:t 4off /0;
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Colligative Properties of Electrolyte +olutions
le*ation of 'oilin" Point
ET# B m 9#Ghere m B molality
(5olality is moles of solute per kilo"ram of sol*ent)
The ffect of ,issociation
ET# B i m 9#i B the num#er of particles released into the
solution per formula unit of solute
e.g.' =aCl dissociates into i 5 <
e.g.' =a dissociates into i 5 1
< =a? ? / +O>-
e.g.' acetic acid a wea& acid and wea&
electrolyte! does not dissociate i 5 /
alsoDepression of
,ree)ing Point
ETf B m 9f
ETf B i m 9f
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:#i+# aueous solution "ould be e$pe+ted to #avet#e #ig#est boiling point
2/ >%2>> m EaCl
4/ >%2>> m CaCl4
B/ >%>> m Fe)EO
B/
B
%>> m Fe)EOB/4
?/ >%>> m Co)SO
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:#i+# aueous solution "ould be e$pe+ted to #ave t#e#ig#est boiling point
2/ >%2>> m EaCl ET# B )4/)>%2>>/ 9# ' >%4>> 9#
4/ >%2>> m CaCl4 ET# B )B/)>%2>>/ 9# ' >%B>> 9#
/) 0.0 m Fe)EOB/4 ET# B )B/)>%>>/ 9# ' >%4 9#
?/ >%>> m Co)SO%>>/ 9# ' >%2> 9#
le*ation of 'oilin" Point
The ffect of ,issociation
ET# B i m 9#
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ColloidsH Colloidal ,ispersions
Colloids are lar"e particles dispersed insolution 4 1nm to 1000 nm in si+e 4 .". :lo#ular proteins &00 nm
3amples 4 pal (ater in solid Si2)
4 !erosols (li>uids in :as) 4 Smoke (solids in !ir) 4 5ilk (fat droplets I solids in ater) 4 5ayonnaise (ater droplets in oil)
4 Paint (solid pi"ments in li>uid) 4 'iolo"ical fluids (proteins I fats in ater)
Characteristics 4 =ar"e particle si+e colloidsH translucent cloudy
milky) 4 Small particle si+e colloidsH can #e clear
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Colloidal ,ispersions
4 Tyndall ffect =i"ht Scatterin"
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