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Solutions

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 Types of solutions

Solute

Solvent

SolutionPhase

Examples

Gas Gas Gas Air, natural gas

Gas Liquid Liquid Club soda (CO2 in H2O), artiial blood

(O2

 in per!uorodealin)

Liquid Liquid Liquid "od#a

Solid Liquid Liquid Saline

Gas Solid Solid H2$%d

Solid Solid Solid &'#arat gold (Ag in Au)

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nergetis of solutionfor*ation

• &) %ure sol+ent  separated sol+ent *oleules

 – ∆H&- beause inter*oleular fores are being

bro#en

•

2) %ure solute

 separated solute *oleules – ∆H2- beause inter*oleular fores are being

bro#en

• .) Separated sol+ent and solute *oleules  solution

 – ∆H./- beause inter*oleular fores are being

for*ed

∆Hsolution0∆H&1∆H21∆H.

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3at it *eans to be ideal

• 4or ondensed p3ases, 5e #no5 t3at t3ereare inter*oleular fores, 53i3 *ay befairly signiant6 Considering t3e ase of

 7ust t5o di8erent types of *oleules in asolution (A and 9), t3ere are really three types of interations: AA, A9 and 996

• ;f t3e solution is ideal, t3en t3e

*agnitudes of t3ese interations are allequal < i6e6 it doesn=t really *atter 53oyour neig3bor is>

•   ∆Hsolution 0 -,

∆"solution 0 -

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3at it *eans to be nonideal

• ;nter*oleular fores bet5een solute and sol+ent*oleules are stronger t3an ot3er inter*oleularfores

 – ∆H.∆H&1∆H2

 – ∆Hsolution /-, ∆"solution /-

• ;nter*oleular fores bet5een solute and sol+ent*oleules are 5ea#er t3an ot3er inter*oleularfores

 – ∆H./∆H&1∆H2

 – ∆Hsolution -, ∆"solution -

 – ;f fores are *u3 5ea#er, t3en a solution *ay not for*at all>

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?aoult=s La5

• Consider a solution *ade up of sol+ent A(large purple sp3eres) and solute 9 (s*allgreen sp3eres)6

•  T3e rate at 53i3 A lea+es t3e surfae

(+apori@ation) is proportional to 3o5 *anyyou 3a+e on t3e surfae, 53i3 is

proportional to t3e *ole fration: r0#A

•  T3e rate at 53i3 A o*es ba#(ondensation) is proportional to t3eonentration of t3e gas, 53i3 is

proportional to t3e partial pressure: r0#=%A• Sine t3ese t5o rates *ust be t3e sa*e:

6

4or a pure liquid A0& so #$#=0%AB6 T3is *eans

t3at

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;deal solutions

• An ideal solution is one 53ere?aoult=s La5 is obeyed6

• Sine %0%A1%9, and t3e +apor

pressure for a liquid is t3esa*e as t3at for a gas, for anideal solution 5e an say t3at

• 4urt3er*ore, sine A190&,

or

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a*ple of an ideal solution

• Solutions tend to be3a+eideally 53en t3e sol+ent (A)

and solute (9) are si*ilarDto ea3 ot3er in ter*s of*oleular struture, polarity,inter*oleular fores, et6

• 6 9en@ene and toluene(*et3ylben@ene)

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a*ple of a nonidealsolution

• Signiant de+iations fro*?aoult=s La5 (eept for

dilute solutions)•  Typially ta#es plae 53en

solute and sol+ent aredissi*ilar

• 6 Carbon disulde (CS2)

and aetone (2propanone)

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Co*parison of solutionbe3a+ior

• Fotie t3at in t3e li*it of+ery +ery onentrated

solutions of 9, real solutionsapproa3 ?aoult=s La56

• 4or dilute solutions of 9, t3ereal solution 5ill also

approa3 Henry=s La56

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a*ple

•  T3e +apor pressure of pure 5ater at2-6- oC is &6 **Hg6 3at is t3e+apor pressure at 2-6- oC abo+e a

solution t3at 3as -62- *ol C&2H22O&& 

(surose) and 6- g CO(FH2)2 (urea)

dissol+ed per #ilogra* of 5aterI

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Solution

• 4irst nd t3e *oles of urea: n 0 6-g $ J-6-J g$*ol 0 &62 *ol urea

• Fet nd t3e *oles of 5ater: n 0&--- g $ &K6-2 g$*ol 0 6 *ol5ater

• Fo5 deter*ine t3e *ole fration of

5ater:

• 4inally, use ?aoult=s la5 to alulatet3e +apor pressure of t3e 5ater

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a*ple

•  T3e +apor pressures of ea3 o*ponent in a *iture ofpropanone (aetone, A) and tri3loro*et3ane (3lorofor*,C) 5ere *easured at .oC 5it3 t3e follo5ing results:

• Conr* t3at t3e *iture onfor*s to ?aoult=s La5 for t3e

o*ponent in large eess and to Henry=s La5 for t3e*inor o*ponent6 4ind t3e Henry=s La5 onstants6

xC   0 0.20 0.40 0.60 0.80 1

%C (torr) - .6. K26 &'2 2-- 2.

%A 

(torr) .' 2- & 26. .J6K -

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Solution

• ;t is usually a good idea to plot t3edata rst6

• 4or ?aoult=s la5, 5e need to loo# at

t3e t5o etre*es (C

- and C

&)64or bot3 substanes (A and C) itappears t3at t3e data approa3 t3eirorreponding li*its (%AB and %CB)

• 4or Henry=s la5, 5e need to loo# at

t3e sa*e li*its and t to a straig3tline6 4or A, 5e need t3e slope asC&, 53i3 is approi*ately 2.6.

#%a6 4or C, 5e need t3e slope asC-, 53i3 is approi*ately 226-

#%a6

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%ressureo*positiondiagra*s

• e 3a+e already seen 3o5 todeal 5it3 binary *itures6

•

;f 5e assu*e an idealsolution, t3en t3e +aporpressure of ea3 o*ponent5ill be gi+en by ?aoult=s la5:

•  T3us t3e total pressure 5illbe: or

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%ressureo*positiondiagra*s

• 3at about t3e +aporI T3e *ore+olatile o*ponent (3ig3er "%)s3ould be present in greaterquantities in t3e gas p3ase6

• Msing Nalton=s la5,

• Sine t3e total pressure *ust bet3e sa*e as t3e +apor pressure (atequilibriu*), for an ideal solution5e an say t3at:

 – Fotie t3at if %AB$%9B&, t3en yAA

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%ressureo*positiondiagra*s

• e an also rearrange t3eseequations to sol+e for t3e total

pressure (%A1%9) as a funtionof t3e o*position in t3e gasp3ase (rat3er t3an t3e liquidp3ase):

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4ree@ing point depression and

boiling point ele+ation

• Consider solutions 53ereonly t3e sol+ent is +olatile,and t3e solute onlydissol+es in t3e liquidp3ase of t3e sol+ent

•   ∆ Tf  0 iE f m

•   ∆ Tb 0 iE bm

i 0 +an=t Ho8 fator (i 0 & fora noneletrolyte, & for a

5ea# eletrolyte, or P ofpartiles for a strongeletrolyte)

E f  0 free@ingpoint

depression (ryosopi)

onstantE b 0 boilingpoint ele+ation

(ebulliosopi) onstant

m 0 *olality

3ttps:$$5556boundless6o*$3e*istry$solutions$olligati+epropertiesnoneletrolytesolutions$free@ingpointdepression$

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a*ple

• 3at is t3e free@ing point of anaqueous surose solution t3at 3as26- g C&2H22O&& per &--6- g H2OI

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Solution

• 4irst nd t3e nu*ber of *oles of surose: n0 26- g $ .'26. g$*ol 0 -6-.- *ol surose

• Fet nd t3e *olality of t3e solution: m 0

-6-.- *ol $ -6&--- #g H2O 0 -6.- m• Fet deter*ine t3e 3ange in free@ing point:∆ Tf  0 iE f m 0 &(&6KJ oC$m)(-6.- m) 0

&6.J oC

• Sine t3e nor*al free@ing point of 5ater is -oC, t3e ne5 free@ing point 5ill be (-1 &6.J)oC, or &6.J oC

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Os*oti pressure

• Os*osis net !o5 of sol+ent*oleules t3roug3 ase*iper*eable *e*brane – Sol+ent *oleules go fro* a

solution of lo5er onentrationto a solution of 3ig3eronentration (solute is notable to pass t3roug3)

• Os*oti pressure (Π) 0

pressure required to stopos*osis

•   Π 0 Q?T, 53ere Q 0 *olarity

3ttp:$$3e*istry6tutor+ista6o*$p3ysial3e*istry$os*otipressure63t*l

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a*ple

• An aqueous solution is prepared bydissol+ing &6- g of 3e*oyanin, aprotein obtained fro* rabs, in -62-

L of 5ater6 T3e solution 3as anos*oti pressure of -6--.'2 at* at2E6

• A) 3at is t3e *olar *ass of3e*oyaninI

• 9) 3at s3ould t3e free@ing point of

t3e solution beI

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Solution (part a)

• Msing t3e os*oti pressure, 5e annd t3e *olarity of t3e solution:π0Q?T so Q0π$?T

• Fet nd t3e *oles of 3e*oyanin:Q0n$" so n0Q"

• 4inally, nd t3e *olar *ass:n0*$QQ so QQ 0 *$n (QQ 0 *olar*ass)

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letrolyti solutions

• Feed to ta#e into aount t3e total iononentration

 – 4or strong (dilute solutions of) eletrolytes you anuse stoi3io*etry

 – 4or 5ea# eletrolytes you an use equilibriu*(o*ing soon>)

• +an=t Ho8 fator (i) < orretion for olligati+eproperties of eletrolytes

∆ Tf  0 iE f m

∆ Tb 0 iE bm

Π 0 iQ?T