KI1101-2012-KD Lec07 IntermolecularAttractions

8/10/2019 KI1101-2012-KD Lec07 IntermolecularAttractions

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Chapter 12:Intermolecular Attractions

and the Properties of Liquids

and SolidsChemistry: The Molecular Nature

of Matter, 6E

Jespersen/Brady/yslop



Chemistry! Stucture and "eacti#ity! Bodner



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $

Chapter 12 Intermolecular Forces

Important differences %et&een 'ases!

solids! and liquids: Gases

()pand to fill their container

Liui!s "etain #olume! %ut not shape

"oli!s

"etain #olume and shape



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *

Chapter 12 Intermolecular Forces

#hysical "tate of molecule !epen!s on

A#era'e +inetic ener'y of particles "ecall ,( -a#e

Intermolecular .orces

(ner'y of Interparticle attraction #hysical #roperties of Gases, Liui!s

an! "oli!s !etermine! $y

o& ti'htly molecules are pac+ed to'ether Stren'th of attractions %et&een

molecules



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0

Con#ertin' %as liui! or soli!

olecules must 'et closer to'ether Cool or compress

Con#ertin' liui! or soli! %as

"equires molecules to mo#e farther apart eat or reduce pressure

As -! ,inetic (ner'y of molecules

At certain -! molecules dont ha#eenou'h ener'y to %rea+ a&ay from oneanothers attraction

Intermolecular &ttractions




Inter 's( Intra)Molecular Forces Intramolecular forces

Co#alent %onds &ithin molecule Stron' %ond 4Cl5 6 *$1 +J/mol

Intermolecular forces Attraction forces %et&een molecules 7ea+ #apori8ation 4Cl5 6 13 +J/mol

Cl H Cl H

Covalent Bond (strong) Intermolecular attraction 4&ea+5


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Electrone%ati'ity *e'ie+Electrone%ati'ity: easure of attracti#e

force that one atom in a co#alent %ond hasfor electrons of the %ond


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on! -ipoles

-&o atoms &ith different electrone'ati#ity#alues share electrons unequally

(lectron density is une#en i'her char'e concentration around more

electrone'ati#e atom on! !ipoles

Indicated &ith delta 4;5 notation

Indicates partial char'e has arisen

H F


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Net -ipoles

"ymmetrical molecules (#en if they ha#e polar %onds Are non)polar %ecause %ond dipoles cancel

&symmetrical molecules

Are polar %ecause %ond dipoles do not cancel -hese molecules ha#e permanent! net !ipoles

Molecular !ipoles

Cause molecules to interact =ecreased distance %et&een molecules increasesamount of interaction


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Intermolecular Forces

7hen su%stance melts or %oils Intermolecular forces are %ro+en ?ot co#alent %onds

"esponsi%le for non)i!eal %eha#ior of

'ases "esponsi%le for e)istence of condensed

states of matter

"esponsi%le for %ul+ properties of matter Boilin' Points and eltin' Points "eflect stren'th of intermolecular forces



Three Important Types ofIntermolecular Forces

1@ =ipoledipole forces ydro'en %onds

2@ London dispersion forces$@ Iondipole forces

Ioninduced dipole forces



I( -ipole)!ipole &ttractions ccur only %et&een polar

molecules Possess dipole moments

olecules need to %e

close to'ether Polar molecules tend toali'n their partial char'es to

As dipole moment !intermolecular force

+ +

+ +

+ +


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I( -ipole)!ipole &ttractions

-um%lin' molecules i)ture of attracti#e and

repulsi#e dipoledipoleforces

Attractions 4 5 'reaterthan repulsions4 5

Det net attraction E 1F of co#alent %ond


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-ipole ) -ipole &ttractions

Interactions %et&een net dipoles in polarmolecules A%out 1F as stron' as a co#alent %ond

=ecrease as molecular distance increases =rops off as 1/d $ 4d 6 distance %et&een

dipoles5

=ipoledipole forces &ith polarity



.y!ro%en on!s Special type of =ipole=ipole Interaction

Gery stron' dipoledipole attraction E*> +J/mol

ccurs %et&een . and hi'hly electrone'ati#e atom4/, N, or F5 H.! H! and H? $on!s 'ery polar

e s lie closer to than to ! so hi'h partial char'es only has 1 e! so

0. presents almost %are proton

almost

full 1 char'e (lements small si8e! means hi'h char'e density Positi#e end of one can 'et #ery close to ne'ati#e end of

another



Eamples of .y!ro%en on!in%

H O

H

H O

H

H O

H

H N

H

H

H F H O

H

H F H N

H

H

H N

H

H

H N

H

H

H N

H

H

H O

H



Effects of .y!ro%en on!in%

Boilin' points of compounds ofelements of DroupsIGA! GA! GIA! and

GIIA@ Boilin' points ofmolecules &ith %ondin' are hi'her

than e)pected@ =ont follo& rule that

BP as 4London forces 5

B oi l i n gP o

i n t ( ° C )



.y!ro%en on!in% in 3ater

"esponsi%le for e)pansion of &ater as it free8es

ydro'en %ondin' produces stron' attractions inliquid

ydro'en %ondin' 4dotted lines5 %et&een&ater molecules in ice form tetrahedral confi'uration


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II( Lon!on -ispersion Forces Intermolecular forces %et&een

nonpolar molecules -&o neutral molecules 4atoms5can affect each other ?ucleus of 1 molecule 4atom5

attracts es of adacent molecule4atom5 (lectron cloud distorts -emporary or instantaneous

!ipole forms ne instantaneous dipole can

induce another in adacent molecule4atom5

"esults in net attracti#e force

e

e

2+

e

e

Electrostaticattraction

He atom 1 He atom 2

2+


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Lon!on Forces 7hen atoms near one another!

their #alence electrons interact "epulsion causes electron clouds

in each to distort and polari8e

Instantaneous! in!uce!!ipoles result from thisdistortion (ffect enhance! &ith increase!

particle mass

(ffect !iminishe! %y increase! !istance %et&een particles



Lon!on -ispersion Forces

Instantaneous dipoleinduced dipoleattractions Lon!on -ispersion Forces

Lon!on forces

-ispersion forces

=ecrease as 14! 6 4d 6 distance %et&eenmolecules5

perate %et&een all molecules ?eutral or net char'ed ?onpolar or polar




Lon!on -ispersion Forces

(ase &ith &hich dipole moments can %einduced and thus London =ispersion.orces depends on

1( #olari5a$ility

2( Molecular si5e

?um%er atoms olecular mass

1( Molecular "hape



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 2$

1( #olari5a$ility

(ase &ith &hich electrondistri%ution in neutral atom4or molecule5 can %e distorted

Lar'er molecules 6 more polari8a%le Lar'er num%er of e s 'reater ease of

distortin' electron cloud a'nitude of resultin' partial char'e is lar'er

London .orces as ore e! less ti'htly held

London .orces as electron cloud #olume

=epends on si8e of atoms






Ta$le 12(1 oilin% #oints of .alo%ensan! No$le Gases

Larger molecules have stronger London forcesand thus higher boiling points.






.o+ Intermolecular Forces-etermine #hysical #roperties

#ropane, C8

.9

BP *2@1oC

.eane, C6.1

BP 3@9oC ore sites 4mar+ed &ith K5 alon' its chain &hereattraction to other molecules can occur




8( Molecular "hape

Increased surface area a#aila%le for contact

6 Increased London .orces London dispersion forces %et&een spherical

molecules are lo+er than chain)li;e

molecules ore compact molecules s not as free to interact &ith s on other

molecules Less compact molecules s ha#e more chance to interact &ith s

on other molecules





Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E

our Turn77hich species has a hi'her %oilin' point! Cl2 or

Cl .2 or . M

A@ Cl .2

B@ Cl2 .2

C@ Cl .=@ Cl

2 .

$>



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $1

III( Ion)!ipole &ttractions Attractions %et&een ion and char'ed end of

polar molecules Attractions can %e quite stron' as ions ha#e full

char'es

(a) ,egative ends of ater dipoles surround cation

(b) Positive ends of ater dipoles surround anion




E( Ion)!ipole &ttractions &lCl8<6.2/

Positive charge of -l%+ ionattracts partial negativecharges on of ater

molecules on/dipole attractions hold

ater molecules to metalion in h0drate 1ater molecules are found

at vertices of octahedronaround aluminum ion

Attractions %et&een ion and polar molecules



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $$

Ion)in!uce! -ipole &ttractions

Attractions %et&een ion and dipole it induceson nei'h%orin' molecules =epends on

Ion char'e an! Polari8a%ility of its nei'h%or

Attractions can %e quite stron' as ion char'e does?- flic+er on and off li+e instantaneous dipoles of

ordinary London forces E( I and Ben8ene

" f I t l l



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $*

"ummary of Intermolecular &ttractions

-ipole)!ipole occur %et&een neutral molecules &ith permanent

dipoles a%out 1F 0F of co#alent %ond id ran'e in terms of intermolecular forces.y!ro%en $on!in%

Special type of dipoledipole interaction

ccur &hen molecules contain ?H!H. and H %onds

A%out 0F to 1>F of a co#alent %ond

" f I t l l




"ummary of Intermolecular &ttractions

Lon!on !ispersion Present in all su%stances 7ea+est intermolecular forces 7ea+! %ut can lead to lar'e net attractions

Ion)!ipole ccur &hen ions interact &ith polar molecules Stron'est intermolecular attraction

Ion)in!uce! !ipole ccur &hen ion induces dipole on nei'h%orin' particle =epend on ion char'e and polari8a%ility of its nei'h%or




=sin% Intermolecular Forces

ften can predict physical properties 4li+e BP

and P5 %y comparin' stren'ths ofintermolecular attractions Ion=ipole

ydro'en Bondin' =ipole=ipole London =ispersion .orces

Lar'er! lon'er! hea#ier molecules ha#e stron'erI.s

Smaller! more compact! li'hter molecules ha#e

&ea+er I.s

1ea2est

3trongest




Learnin% Chec; Identify the +inds of intermolecular forces present

in the follo&in' compounds "an+ them in order of increasin' %oilin' point:

2S! C$! CBr*! and ?e

H

3

H

H

C

4H

HH

Br

CBr Br

Br

,e

dipoledipole ydro'en%ondin' Londonforces

Londonforces

6$$1@3

62>@2

C$ N2S N CBr* N ?e



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $

#hysical #roperties that -epen! on.o+ Ti%htly Molecules #ac;

Compressi$ility easure of a%ility of su%stance to %e forced into

smaller #olume

=etermined %y stren'th of intermolecular forces Dases hi'hly compressi$le olecules far apart 7ea+ intermolecular forces

Solids and liquids nearly incompressi$le olecules #ery close to'ether Stron'er intermolecular forces

l l i



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $<

Intermolecular Forces -etermine"tren%th of Many #hysical #roperties

*etention of >olume an! "hape "oli!s +eep %oth 'olume and shape

Stron'est intermolecular attractions

olecules closest Gases! +eep nothin'

7ea+est intermolecular attractions olecules farthest apart

Liui!s +eep 'olume! %ut not shape Attractions intermediate



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *>

-iffusion o#ement that

spreads one 'asthou'h another 'as tooccupy spaceuniformly

Spontaneousintermin'lin' ofmolecules of one 'as&ith molecules ofanother 'as

4ccurs more rapidl0 in gases than in li5uids Hardl0 at all in solids

In Gases



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *1

-iffusion In Gases

olecules tra#el lon'distances %et&eencollisions

=iffusion rapid In Liui!s

olecules closer

(ncounter morecollisions -a+es a lon' time to

mo#e from place toplace

In "oli!s =iffusion none)istent at

room temp 7ill at hi'h -emp

" f T i




"urface Tension

7hy does 2 %ead up

on a freshly &a)ed carinstead of formin' alayerM

Inside %ody of liquid Intermolecular forces in

all directions olecules at surface

I. only pull do&n andto side .e&er attractions! so

free to e)pand indirection &ith no forces

" f T i



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *$

"urface Tension

-endency of liquid

to ta+e shape thatminimi8es surfacearea

olecules at surfaceha#e hi'her potentialener'y than those in%ul+ of liquid

(ner'y required toe)pand or increasesurface %y unit area

7a) 6 nonpolar 2 6 polar

7ater %eads as &antsto ma)imi8eattractions

"urface Tension



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E **

"urface Tension Liquids containin'

molecules &ith stron'intermolecular forces ha#ehi'h surface tension Allo&s us to fill 'lass a%o#e

rim Di#es surface rounded

appearance

Surface acts as Os+in that lets&ater pile up Surface resists e)pansion and

pushes %ac+

3urface 6ension as F

3urface 6ension as F

3 tti




3ettin%

A%ility of liquid to spread

across surface to formthin film Dreater similarity in

attracti#e forces

%et&een liquid andsurface! yields 'reater&ettin' effect

ccurs only if

intermolecular attracti#eforce %et&een surfaceand liquid a%out asstron' as &ithin liquid

itself

3ettin%




3ettin%E@ 2 &ets clean 'lass surface as it forms

%onds to Si2 surface =oes not &et 'reasy 'lass! as 'rease interacts

&ea+ly &ith &ater nly London dispersion forces .orms %ead instead

"urfactants

Added to deter'ents to lo&er surface tension of 2

?o& &ater can 'et %etter access to surface to %ecleaned

"urfactants




"urfactants Su%stances that ha#e polar and nonpolar

characteristics Lon' chain hydrocar%ons &ith polar tail

434

4 ,a+

4

4

4,a+

?onpolar end interacts &ith 'rease Polar end interacts &ith 2

-hus increasin' solu%ility of 'rease in &ater

>i it




>iscosity "esistance to flo& easure of fluids

resistance to flo& orchan'in' form Lar'er molecules collide

and interact moreoften! impedin' theirflo&

-lso called internal friction 7epends on intermolecular attractions olecular shape

&&&@chemistrye)plained@com

>i it



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *<

>iscosity Giscosity &hen -emperature

ost people associate liui!s &ith #iscosity olasses more #iscous than &ater

Dases ha#e #iscosity

"espond almost instantly to formchan'in' forces Solids! such as roc+s

?ormally respond #ery slo&ly to forces actin' to

chan'e their shape .or same si8e molecules! 'iscosity

increases as stren%th of Intermolecular

Forces increases

Effect of Intermolecular Forces on



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0>

Effect of Intermolecular Forces on >iscosity

&cetone

Polar molecule =ipoledipole and London forces

Ethylene %lycol

Polar molecule

ydro'en%ondin' =ipoledipole and London forces

1hich is more viscous88

our Turn7




our Turn7.or each pair 'i#en! &hich is more #iscose M

C$C2C2C2! C$C2C2C C31*! C1223 ?$4l 5! P$4l 5

A@ C$C2C2C2 C31* ?$4l 5B@ C$C2C2C2 C1223 ?$4l 5

C@ C$C2C2C C31* P$4l 5=@ C$C2C2C C1223 ?$4l 5

(@ C$C2C2C2 C1223 P$4l 5

01

"olu$ility




"olu$ility OLi;e !issol'es li;e

-o dissol#e polar su%stance! use polar sol#ent -o dissol#e nonpolar su%stance! use nonpolarsol#ent

Compare relati#e polarity of t&o su%stances Similar polarity means 'reater a%ility to interact

&ith each other =ifferin' polarity means that they dont interact

mo#e past each other "urfactants

Both polar and nonpolar characteristics

Qsed to increase solu%ility




our Turn7

7hich of the follo&in' are not e)pectedto %e solu%le in &aterM A@ .

B@ C*

C@ C$

=@ All are solu%le

#h Ch



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0*

#hase Chan%es

Chan'es of physical state =eal &ith motion of molecules

As temperature chan'es atter &ill under'o phase chan'es

Liui! Gas (#aporation As heat 2! forms steam or &ater #apor

"equires ener'y or source of heat to occur



*ate of E'aporation




*ate of E'aporation =epends on

-emperature Surface area Stren'th of

intermolecularattractions

olecules that escapefrom liquid ha#e lar'erthan a#era'e ,(s

7hen they lea#e A#era'e ,( of

remainin' moleculesis less

- lo&er

Effect of Temperature on E'aporation




Effect of Temperature on E'aporation*ate

.or 'i#en liquid "ate of e#aporation per

unit surface area as-

7hyM At hi'her -! total

fraction of molecules&ith ,( lar'e enou'h to

escape is lar'er "esult: rate of

e#aporation is lar'er

?inetic Ener%y -istri$ution in T+o




?inetic Ener%y -istri$ution in T+o-ifferent Liui!s

Smaller I.s Lo&er ,( required to

escape liquid & e#aporates faster

Lar'er I.s i'her ,( required

to escape liquid e#aporates slo&er

- B

Chan%es /f "tate In'ol'e Euili$ria



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0<

Chan%es /f "tate In'ol'e Euili$ria

.raction of molecules in condensed state is

hi'her &hen intermolecular attractions arehi'her Intermolecular attractions must %e o#ercome

to separate the particles! &hile separatedparticles are simultaneously attracted to oneanother

condensedphase separatedphase

efore "ystem *eaches




efore "ystem *eachesEuili$rium

Liquid is placed inempty container Be'ins to e#aporate

nce in 'as phase olecules can

con!ense %y

Stri+in' surface of liquidand 'i#in' up some+inetic ener'y

"ystem &t Euili$rium




"ystem &t Euili$rium

"ate of e#aporation 6rate of condensation Can occur in system

&here molecules areconstrained to remainclose to liquid surface

"imilar Euili$ria *eache! in




"imilar Euili$ria *eache! inMeltin%

Meltin% #oint @mpA Solid %e'ins to chan'e

into liquid as heat added -ynamic Euili$ria

e)ists %et&een solid andliquid states Meltin% 4re! arro&s5 and

free5in% 4$lac; arro&s5occur at same rate

As lon' as no heat added orremo#ed from equili%riummi)ture

Euili$ria *eache! in




Euili$ria *eache! in"u$limation

&t euili$rium

olecules e#aporatefrom solid at same

rate as moleculescondense from #apor

olecules su%lime

and condense oncrystal at same rate

#hase Chan%es




#hase Chan%es

9 n er g 0 of 3 0 s t em

:as

3olid

Li5uid

eltingor Fusion

;apori<ation Condensation

Free<ing

3ublimation7eposition

()othermic! releases heat (ndothermic! a%sor%s heat

Ener%y Chan%es &ccompanyin%




Ener%y Chan%es &ccompanyin%#hase Chan%es

All phase chan'es are possi%le under theri'ht conditions

.ollo&in' sequence is en!othermic

heat soli! melt heat liui! $oil heat %as

.ollo&in' sequence is eothermic

cool %as con!ense cool liui! free5e coolsoli!

. &ccompanyin% #hase Chan%es




. &ccompanyin% #hase Chan%esEn!othermic #hase Chan%es

1@ ust Add eat2@ (ner'y enterin' system 45Su%limation: . su$ B

Gapori8ation: . 'ap B

eltin' or .usion: . fus B

Eothermic #hase Chan%es1@ ust Di#e ff eat

2@ (ner'y lea#in' system 45=eposition: . D

. su$

Condensation: . D

. 'ap

.ree8in': . D

. fus

#hase Chan%es




#hase Chan%es

As - chan'es! matter under'oes phase

chan'es #hase Chan%e

-ransformation from one phase to another

Liui!)>apor Euili$rium Molecules in liui!

?ot in ri'id lattice In constant motion =enser than 'as! so more collisions Some ha#e enou'h +inetic ener'y to

escape! some dont

Liui!)>apor Euili$rium




Liui! >apor Euili$rium

At any 'i#en -!

A#era'e ,inetic(ner'y of moleculesis constant

But ha#e distri%ution

,(s of particles Certain num%er of

molecules ha#eenou'h ,( to escape

surface Process is (#aporation or Gapori8ation As - ! A#'@ ,( and num%er molecules

&ith enou'h ,( to escape

=inetic 9nerg0

F r a c t i on of m o

l e c ul e s

>apor #ressure @>#A




>apor #ressure @>#A Pressure molecules e)ert &hen they e#aporate or

escape into 'as 4#apor5 phase Pressure of 'as &hen liquid or solid is at

equili%rium &ith its 'as phase Increasin' temperature increases #apor pressure

%ecause con#ersion is endothermic liui! 0 heat of 'apori5ation %as↔

Euili$rium >apor #ressure GP once dynamic equili%rium reached Qsually referred to as simply #apor pressure

Measurin% >apor #ressure




Measurin% >apor #ressure

-o measure pressures inside #essels! a manometer isused@

>apor #ressure -ia%ram




>apor #ressure -ia%ram Gariation of

#apor pressure&ith -

Ether

>olatile

i'h #aporpressure near "-

#ropylene%lycol Non)'olatile

Lo& #aporpressure near "-

"- 6 20 C

Effect of >olume on >#




Effect of >olume on ># &( Initial >

Liquid #aporequili%rium e)ists

A. > P

"ate ofcondensation

&( More liui!e'aporates

?e& equili%riumesta%lished

Measurin% .'ap




Measurin% .'ap

ClausisClayperon (quation easure P at #arious -s! then plot

-&o point form of ClausisClayperon (quation easure P at t&o -s and sol#e equation

C

- "

P

#ap

1ln

122

1 11ln

- - "

P

P #ap

Learnin% Chec;




Learnin% Chec;-he #apor pressure of diethyl ether is *>1 mm' at1RC! and its molar heat of #apori8ation is 23+J/mol@ Calculate its #apor pressure at $2RC@

*<2@>10@2<11

10@$>01

5 /4$1*@ /1>3@2

ln*

2

1

, , mol , J

mol J

P

P

122

1 11ln

- - "

P

P #ap

31><@>*<2:@>

2

1 e P P

21

31><@>P P

mm' mm'

P 22 1>3@3

31><@>

*>1

-1 6 29$@10 1 6 2<1@10,

-2 6 29$@10 $2 6 $>0@10,

our Turn7




our Turn7=etermine the enthalpy of #apori8ation! in

+J/mol! for %en8ene! usin' the follo&in'#apor pressure data@ - 6 3>@3 C P 6 *>> torr - 6 >@1 C P 6 93> torr

A@ $2@2 +J/molB@ 1*@> +J/mol

C@ $2@* +J/mol=@ >@$2 +J/mol(@ 1*@> +J/mol

90

our Turn7 ) "olution




ou u "o ut o

93

1

2 2 1

1 1ln

*>> ' 1 1lnJ93> ' $0$@1 , $$$@3 ,

:@$1*, mol

$2!2$0 J/mol or $2@2 +J/mol

#ap

#ap

#ap

P

P " - -

mm mm

D æ ö= -ç ÷

è ø

D æ ö= -ç ÷è ø

D =

-o "oli!s .a'e >apor #ressures




p

es

At 'i#en - Some solid particles ha#e enou'h ,( so escapeinto #apor phase

7hen #apor particles collide &ith surface they can %e captured

Euili$rium 'apor pressure of soli! P of #apor in equili%rium &ith solid








Boilin' points of compounds of elementsof Droups IGA! GA! GIA!and GIIA@

Boilin' points ofmolecules &ith %ondin' are hi'herthan e)pected

=ont follo& rule that

BP as

4Londonforces 5

our Turn7



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E >

our Turn7

7hich of the follo&in' &ill affect the %oilin'

point of a su%stanceM A@olecular mass of the materialB@Intermolecular attractions

C@-he e)ternal pressure on the material=@All of these(@?one of these

.eatin% Cur'e




.eatin% Cur'e eat added at constant rate

7iagonal lines Heating of solid> li5uid or gas

Hori<ontal lines Phase changes elting point Boiling point

Coolin% Cur'e




Coolin% Cur'e

eat remo#ed at constant rate

7iagonal lines Cooling of solid>

li5uid or gas

Hori<ontal lines Phase changes elting point Boiling point

3upercooling 6 of li5uid dips belo its free<ing point

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o& much heat! in J! is required to con#ert

1>@>> ' of ice at 1>@>>o

C to &ater at 0>@>> oC M Specific heat 4J/' ,5: ice! 2@1>! &ater! 1@*9

(nthalpy of fusion 6 3@>1> +J/mol0* A@ 0*$ JB@ 03*$ J

C@ 2$>* J=@ 2$3* J(@ 32!*>> J

$

Ener%ies of #hase Chan%es




% %

()pressed per mole

Molar heat of fusion 4fus5 heat a%sor%ed %y 1 mole of solid &hen it melts to 'i#e

liquid at same - and P

Molar heat of 'apori5ation 4#ap 5 heat a%sor%ed &hen 1 mole of liquid is chan'ed to 1 mole

of #apor at constant - and P

Molar heat of su$limation 4su% 5

eat a%sor%ed %y 1 mole of solid &hen it su%limes to 'i#e1 mole of #apor at constant - and P All of these quantities tend to &ith in'

intermolecular forces

Le Chateliers #rinciple




p (quili%ria are often distur%ed or upset

7hen dynamic equili%rium of system is upset%y a distur%ance System responds in direction that tends to

counteract distur%ance and! if possi%le! restoreequili%rium

#osition of euili$rium used to refer to relati#e amounts of su%stance on

each side of dou%le 4equili%rium5 arro&s

Liui! >apor Euili$rium




p Liui! 0 .eat >apor

in' - s amount of #apor

s amount of liquid Euili$rium has shifte!

6 ri'ht shift more #apor is produced at e)pense of liquid

-emperaturepressure relationships can %e

represented usin' a phase !ia%ram

#hase -ia%rams




% Sho& the effects of %oth pressure and temperature

on phase chan'es Boundaries %et&een phases indicate equili%rium Triple point:

the temperature and pressure at &hich s ! l ! and % are all

at equili%rium Critical point :

the temperature and pressure at &hich a 'as can nolon'er %e condensed

-C 6 temperature at critical point

PC 6 pressure at critical point

#hase -ia%ram ais 6 temperature




% ais temperature ais 6 pressure

As P 4- const5! solidmost li+ely

ore compact As - 4P const5! 'as

most li+ely i'her ener'y (ach point 6 - and P

B 6

( 6 . 6

E

>@>1RC! *@0 torr

1>>RC! 93> torr 1>RC! 2@10 torr

F

#hase -ia%ram of 3ater



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <

% & 6 #apor pressure

cur#e for ice - 6 #apor pressure

cur#e for liquid &ater C 6 meltin' point line

6 triple point 6 -&here all $ phases inequili%rium

- 6 critical point

- and P a%o#e &hichliquid does not e)ist

Case "tu!y: &n Ice Nec;lace



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <>

A cu%e of ice may %esuspended on a strin' simply%y pressin' the strin' into theice cu%e@ As the strin' ispressed onto the surface! it%ecomes em%edded into theice@

7hy does this happenM

#hase -ia%ram H C/2



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <1

% 2

?o& line%et&een solidand liquidslants to ri'ht

ore typical

7here is -riplepointM

7here isCritical pointM

"upercritical Flui!




Su%stance &ith temperature a%o#e its criticaltemperature 4T

C5 and density near its liquid

density a#e unique properties that ma+e them

e)cellent sol#ents Galues of TC tend to &ith increased

intermolecular attractions %et&een particles



Types of "oli!s



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <*

Crystalline "oli!s

Solids &ith hi'hly re'ular arran'ements ofcomponents

&morphous "oli!s

Solids &ith considera%le disorder in theirstructures

Crystalline "oli!s




=nit Cell

Smallestse'ment thatrepeats re'ularly

Smallestrepeatin' unit oflattice

2=imensional

Qnit Cells

Crystal "tructures .a'e *e%ular# tt




#atterns

Lattice any repeats of unit cell "e'ular! hi'hly

symmetrical system -hree 4$5 dimensional

system of pointsdesi'natin' positions of

components Atoms Ions

olecules

Three Types /f 8)- =nit Cells




Three Types /f 8 - =nit Cells "imple cu$ic

as one host atom at each corner

(d'e len'th a 2r &here r is radius of atom or ion

o!y)centere! cu$ic @CCA as one atom at each corner and one in

center (d'e len'th

Face)centere! cu$ic @FCCA as one atom centered in each face! and

one at each corner

(d'e len'th r22a

$

r*a



T+o 3ays to #ut on 8r! Layer



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <<

1@ =irectly a%o#espheres in 1st layer

2@ A%o#e holes in 1st layer "emainin' holes not

co#ered %y 2nd layer

Cubic lattice? %/dimensional arra0s

8)- "imple Cu$ic Lattice



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>>

Portion of latticeHopen #ie&

Qnit Cell

Space fillin'model

/ther Cu$ic Lattices



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>1

Face Centere!

Cu$ic

o!y Centere!

Cu$ic

Ionic "oli!s




Lattices of Alternatin' char'es

7ant cations ne)t to anions a)imi8es electrostatic attracti#e forces inimi8es electrostatic repulsions

Based on one of three %asic lattices: Simple cu%ic .ace centered cu%ic Body centered cu%ic

Common Ionic "oli!s




*oc; salt or NaCl .ace centered cu%ic lattice of Cl ions 4'reen5 ?a ions 4%lue5 in all octahedral holes

1>$



"paces In Ionic "oli!s &re Fille!3ith Co nte Ions




3ith Counter Ions In ?aCl

Cl ions form facecentered cu%ic unitcell

Smaller ?a ions fillspaces %et&een Cl ions

Count atoms in unitcell a#e 3 of each or

1:1 ?a:Cl ratio

Countin% &toms per =nit Cellf ll




* types of sites in unit cell Central or $o!y position atom is completely contained

in one unit cell Face site atom on face shared %y t&o unit cells E!%e site atom on ed'e shared %y four unit cells Corner site atom on corner shared %y ei'ht unit cells

Site Counts as Shared b ! unit cells

Bod0 1 1

Face 1"2 29dge 1"# #

Corner 1"$ $

Eample: NaCl




"ite J of Cl

Body 1 >

.ace >

(d'e

! $3 21

! $12 *1

! 1 :1

Face9dge Corner

Center

Learnin% Chec;:= i h % f h f i i




!?!CsCl

=etermine the num%er of each type of ion inthe unit cell@

?@n3

?&CaF$

"ome Factors &ffectin%C t lli "t t



Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1><

Crystalline "tructure

Si8e of atoms or ions in#ol#ed Stoichiometry of salt aterials in#ol#ed

Some su%stances do not form crystalline solids

&morphous "oli!s @GlassA




a#e little order! thus referred to as Osuper

cooled liquids (d'es are not clean! %ut ra''ed due to the lac+

of order

)*ay Crystallo%raphy




rays are passed throu'h

crystalline solid Some )rays are a%sor%ed!

most reemitted in all

directions Some emissions %y atoms

are in phase! others out of

phase (mission is recorded on film

)ray -iffraction




9Aperimental 3etup 7iffraction Pattern

Interpretin% -iffraction -ata




As )rays hit

atoms in latticethey are deflected

An'les of

deflections relatedto lattice spacin' So &e can

estimate atomicand ionic radiifrom distance data

Interpretin% -iffraction -ata




ra%% Euation

n K2! sin n 6 inte'er 41! 2! 5 " 6 &a#elen'th ofrays

! 6 interplanespacin' in crystal

# 6 an'le ofincidence and an'leof reflectance ofrays to #ariouscrystal planes

E( 2 -iffraction -ata




-he diffraction pattern of copper metal &as

measured &ith )ray radiation of &a#elen'thof 1@$10 T@ -he first order 4n615 Bra''diffraction pea+ &as found at an an'le theta of0>@0 de'rees@ Calculate the spacin' %et&eenthe diffractin' planes in the copper metal@

!(!.%!# )$DdDsin(#.#)

n" $dsin#

d $.&%

E 8( =sin% -iffraction !ata diff ti t l th t




ray diffraction measurements re#eal thatcopper crystalli8es &ith a facecentered cu%iclattice in &hich the unit cell len'th is $@32 T@7hat is the radius of a copper atom e)pressedin an'stroms and in picometersM

-his is %asically a 'eometry pro%lem@

E(8 @contAPytha'orean theorem: a2 0 $2 c2




A 12@05 A 32@$42dia'onal

dia'onal 6 * r Cu 6 0@12 Tr Cu 6 1@2 T

?o& con#ert to pm

"ecall 1 T 6 1 1>

1>

m and 1 pm 6 1 1>

12

m

pm m

pm

A

m A 12:

1>1

11>12:@1

12

1>

Pytha'orean theorem: a2 0 $2 c2

7here a 6 % 6 $@32 T sides and c 6 dia'onal

2a2 6 c2 and a a c 22 2

Learnin% Chec;

Sil + h i f d %i




Sil#er pac+s to'ether in a faced center cu%ic

fashion@ -he interplanar distance! d!corresponds to the len'th of a side of the unitcell! and is *@>9 an'stroms@ 7hat is the radiusof a sil#er atomM

r a 22r 22 A >9@*

r 6 >@0$3 T

a

Ionic Crystals @e( NaCl, NaN/8A




a#e cations and anions at lattice sites

Are relati#ely hard a#e hi'h meltin' points Are %rittle

a#e stron' attracti#e forces %et&een ions =o not conduct electricity in their solidstates

Conduct electricity &ell &hen molten

"ample .ome+or; #ro$lem




Potassium chloride crystalli8es &ith the roc+

salt structure@ 7hen %athed in rays! thelayers of atoms correspondin' to thesurfaces of the unit cell produce a diffracted

%eam of rays 4U610* pm5 at an an'le of3@<9V@ .rom this! calculate the density4'/cm$5@

12>

our Turn7Witter%ium crystalli8es &ith a face centered




Witter%ium crystalli8es &ith a face centeredcu%ic lattice@ -he atomic radius of Witter%iumis 190 pm@ =etermine the unit cell len'th@

A@ *<0 pmB@ 9>> pmC@ $0> pm

=@ <<> pm(@ 2*9 pm

121

our Turn7 ) "olution




dia'onal of cu%e 6 * &here 6 atomic radius

dia'onal of cu%e 6 2 a &here a 6 side of cu%e

* * ) 190 pma 6 *<0 pm2 2

r r

r = =

Co'alent Crystals Lattice positions occupied %y atoms that are




Lattice positions occupied %y atoms that areco#alently %onded to other atoms atnei'h%orin' lattice sites

Also called net+or; soli!s Interloc+in' net&or+ of co#alent %onds e)tendin'

all directions Co#alent crystals tend to

%e #ery hard

ha#e #ery hi'h meltin' points ha#e stron' attractions %et&een

co#alently %onded atoms

E( Co'alent @Net+or;A "oli!




=iamond 4all C5 sho&n

Si2 silicon o)ide Alternatin' Si and Basis of 'lass and quart8

Silicon car%ide 4SiC5

Metallic Crystals

l d l




Simplest models

Lattice positions of metalliccrystal occupied %y positi#eions

Cations surrounded %y Ocloud

of electrons formed %y #alence electrons e)tends throu'hout entire solid

Metallic Crystals

Cond ct heat and elect icit




Conduct heat and electricity

By their mo#ement! electrons transmit +ineticener'y rapidly throu'h solid

a#e the luster characteristically associated&ith metals 7hen li'ht shines on metal Loosely held electrons #i%rate easily "eemit li'ht &ith essentially same frequency

and intensity

Learnin% Chec;:Classify the follo&in' in terms of most li+ely type of solid@




"u$stance ionic molecular co#alent metallic

: pul#eri8es &hen struc+nonconducti#e of heatand electricity

: 7hite crystalline solid

that conducts electricalcurrent &hen molten ordissol#ed

: shiny! conducti#e!mallea%le &ith hi'h

meltin' temperature

y ' y yp

our Turn7



olecular crystals can contain all of the listed

attraction forces e)cept: A@ =ipoledipole attractionsB@ (lectrostatic forces

C@ London forces=@ ydro'en %ondin'

Documents

KI1101-2012-KD Lec07 IntermolecularAttractions