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Chapter 12:Intermolecular Attractions
and the Properties of Liquids
and SolidsChemistry: The Molecular Nature
of Matter, 6E
Jespersen/Brady/yslop
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Chemistry! Stucture and "eacti#ity! Bodner
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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
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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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3
Inter 's( Intra)Molecular Forces Intramolecular forces
Co#alent %onds &ithin molecule Stron' %ond 4Cl5 6 *$1 +J/mol
Intermolecular forces Attraction forces %et&een molecules 7ea+ #apori8ation 4Cl5 6 13 +J/mol
Cl H Cl H
Covalent Bond (strong) Intermolecular attraction 4&ea+5
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Electrone%ati'ity *e'ie+Electrone%ati'ity: easure of attracti#e
force that one atom in a co#alent %ond hasfor electrons of the %ond
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on! -ipoles
-&o atoms &ith different electrone'ati#ity#alues share electrons unequally
(lectron density is une#en i'her char'e concentration around more
electrone'ati#e atom on! !ipoles
Indicated &ith delta 4;5 notation
Indicates partial char'e has arisen
H F
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Net -ipoles
"ymmetrical molecules (#en if they ha#e polar %onds Are non)polar %ecause %ond dipoles cancel
&symmetrical molecules
Are polar %ecause %ond dipoles do not cancel -hese molecules ha#e permanent! net !ipoles
Molecular !ipoles
Cause molecules to interact =ecreased distance %et&een molecules increasesamount of interaction
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Intermolecular Forces
7hen su%stance melts or %oils Intermolecular forces are %ro+en ?ot co#alent %onds
"esponsi%le for non)i!eal %eha#ior of
'ases "esponsi%le for e)istence of condensed
states of matter
"esponsi%le for %ul+ properties of matter Boilin' Points and eltin' Points "eflect stren'th of intermolecular forces
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Three Important Types ofIntermolecular Forces
1@ =ipoledipole forces ydro'en %onds
2@ London dispersion forces$@ Iondipole forces
Ioninduced dipole forces
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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
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.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
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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
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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 )
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.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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 22
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 2$
1( #olari5a$ility
(ase &ith &hich electrondistri%ution in neutral atom4or molecule5 can %e distorted
Lar'er molecules 6 more polari8a%le Lar'er num%er of e s 'reater ease of
distortin' electron cloud a'nitude of resultin' partial char'e is lar'er
London .orces as ore e! less ti'htly held
London .orces as electron cloud #olume
=epends on si8e of atoms
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 20
Ta$le 12(1 oilin% #oints of .alo%ensan! No$le Gases
Larger molecules have stronger London forcesand thus higher boiling points.
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 29
.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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 2
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
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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 .
$>
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $2
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
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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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $0
"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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $3
=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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $9
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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E $<
Intermolecular Forces -etermine"tren%th of Many #hysical #roperties
*etention of >olume an! "hape "oli!s +eep %oth 'olume and shape
Stron'est intermolecular attractions
olecules closest Gases! +eep nothin'
7ea+est intermolecular attractions olecules farthest apart
Liui!s +eep 'olume! %ut not shape Attractions intermediate
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *>
-iffusion o#ement that
spreads one 'asthou'h another 'as tooccupy spaceuniformly
Spontaneousintermin'lin' ofmolecules of one 'as&ith molecules ofanother 'as
4ccurs more rapidl0 in gases than in li5uids Hardl0 at all in solids
In Gases
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *1
-iffusion In Gases
olecules tra#el lon'distances %et&eencollisions
=iffusion rapid In Liui!s
olecules closer
(ncounter morecollisions -a+es a lon' time to
mo#e from place toplace
In "oli!s =iffusion none)istent at
room temp 7ill at hi'h -emp
" f T i
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *2
"urface Tension
7hy does 2 %ead up
on a freshly &a)ed carinstead of formin' alayerM
Inside %ody of liquid Intermolecular forces in
all directions olecules at surface
I. only pull do&n andto side .e&er attractions! so
free to e)pand indirection &ith no forces
" f T i
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *$
"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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *0
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%
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *3
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *9
"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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *
>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
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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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 02
"olu$ility OLi;e !issol'es li;e
-o dissol#e polar su%stance! use polar sol#ent -o dissol#e nonpolar su%stance! use nonpolarsol#ent
Compare relati#e polarity of t&o su%stances Similar polarity means 'reater a%ility to interact
&ith each other =ifferin' polarity means that they dont interact
mo#e past each other "urfactants
Both polar and nonpolar characteristics
Qsed to increase solu%ility
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0$
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
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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
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*ate of E'aporation
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 03
*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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 09
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$ution in T+o
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0
?inetic Ener%y -istri$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$ria
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0<
Chan%es /f "tate In'ol'e Euili$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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3>
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 31
"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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 32
"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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3$
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3*
#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%
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 30
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! $oil heat %as
.ollo&in' sequence is eothermic
cool %as con!ense cool liui! free5e coolsoli!
. &ccompanyin% #hase Chan%es
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 33
. &ccompanyin% #hase Chan%esEn!othermic #hase Chan%es
1@ ust Add eat2@ (ner'y enterin' system 45Su%limation: . su$ 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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 39
#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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3
Liui! >apor Euili$rium
At any 'i#en -!
A#era'e ,inetic(ner'y of moleculesis constant
But ha#e distri%ution
,(s of particles Certain num%er of
molecules ha#eenou'h ,( to escape
surface Process is (#aporation or Gapori8ation As - ! A#'@ ,( and num%er molecules
&ith enou'h ,( to escape
=inetic 9nerg0
F r a c t i on of m o
l e c ul e s
>apor #ressure @>#A
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3<
>apor #ressure @>#A Pressure molecules e)ert &hen they e#aporate or
escape into 'as 4#apor5 phase Pressure of 'as &hen liquid or solid is at
equili%rium &ith its 'as phase Increasin' temperature increases #apor pressure
%ecause con#ersion is endothermic liui! 0 heat of 'apori5ation %as↔
Euili$rium >apor #ressure GP once dynamic equili%rium reached Qsually referred to as simply #apor pressure
Measurin% >apor #ressure
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 9>
Measurin% >apor #ressure
-o measure pressures inside #essels! a manometer isused@
>apor #ressure -ia%ram
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 91
>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 >#
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 92
Effect of >olume on ># &( Initial >
Liquid #aporequili%rium e)ists
A. > P
"ate ofcondensation
&( More liui!e'aporates
?e& equili%riumesta%lished
Measurin% .'ap
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 9$
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;
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 9*
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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 $2@2 +J/mol
#ap
#ap
#ap
P
P " - -
mm mm
D æ ö= -ç ÷
è ø
D æ ö= -ç ÷è ø
D =
-o "oli!s .a'e >apor #ressures
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 99
p
es
At 'i#en - Some solid particles ha#e enou'h ,( so escapeinto #apor phase
7hen #apor particles collide &ith surface they can %e captured
Euili$rium 'apor pressure of soli! P of #apor in equili%rium &ith solid
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Effects of .y!ro%en on!in%
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 9<
Effects of .y!ro%en on!in%
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
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1
.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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 2
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
our Turn7
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E *
% %
()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$limation 4su% 5
eat a%sor%ed %y 1 mole of solid &hen it su%limes to 'i#e1 mole of #apor at constant - and P All of these quantities tend to &ith in'
intermolecular forces
Le Chateliers #rinciple
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 0
p (quili%ria are often distur%ed or upset
7hen dynamic equili%rium of system is upset%y a distur%ance System responds in direction that tends to
counteract distur%ance and! if possi%le! restoreequili%rium
#osition of euili$rium used to refer to relati#e amounts of su%stance on
each side of dou%le 4equili%rium5 arro&s
Liui! >apor Euili$rium
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 3
p Liui! 0 .eat >apor
in' - s amount of #apor
s amount of liquid Euili$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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 9
% 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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
% 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
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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
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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
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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!
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <2
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
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Types of "oli!s
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <0
=nit Cell
Smallestse'ment thatrepeats re'ularly
Smallestrepeatin' unit oflattice
2=imensional
Qnit Cells
Crystal "tructures .a'e *e%ular# tt
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <3
#atterns
Lattice any repeats of unit cell "e'ular! hi'hly
symmetrical system -hree 4$5 dimensional
system of pointsdesi'natin' positions of
components Atoms Ions
olecules
Three Types /f 8)- =nit Cells
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E <9
Three Types /f 8 - =nit Cells "imple cu$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
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T+o 3ays to #ut on 8r! Layer
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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$ic Lattice
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>>
Portion of latticeHopen #ie&
Qnit Cell
Space fillin'model
/ther Cu$ic Lattices
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>1
Face Centere!
Cu$ic
o!y Centere!
Cu$ic
Ionic "oli!s
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>2
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
*oc; salt or NaCl .ace centered cu%ic lattice of Cl ions 4'reen5 ?a ions 4%lue5 in all octahedral holes
1>$
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"paces In Ionic "oli!s &re Fille!3ith Co nte Ions
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>0
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>3
* 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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>9
"ite J of Cl
Body 1 >
.ace >
(d'e
! $3 21
! $12 *1
! 1 :1
Face9dge Corner
Center
Learnin% Chec;:= i h % f h f i i
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 1>
!?!CsCl
=etermine the num%er of each type of ion inthe unit cell@
?@n3
?&CaF$
"ome Factors &ffectin%C t lli "t t
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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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 11>
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 111
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 112
9Aperimental 3etup 7iffraction Pattern
Interpretin% -iffraction -ata
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 11$
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 11*
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 110
-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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 113
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 119
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 11
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$3 T
a
Ionic Crystals @e( NaCl, NaN/8A
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 11<
a#e cations and anions at lattice sites
Are relati#ely hard a#e hi'h meltin' points Are %rittle
a#e stron' attracti#e forces %et&een ions =o not conduct electricity in their solidstates
Conduct electricity &ell &hen molten
"ample .ome+or; #ro$lem
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E
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@ $0> pm
=@ <<> pm(@ 2*9 pm
121
our Turn7 ) "olution
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 122
dia'onal of cu%e 6 * &here 6 atomic radius
dia'onal of cu%e 6 2 a &here a 6 side of cu%e
* * ) 190 pma 6 *<0 pm2 2
r r
r = =
Co'alent Crystals Lattice positions occupied %y atoms that are
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 12$
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!
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 12*
=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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 120
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
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 123
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@
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Jespersen/Brady/HyslopChemistry:TheMolecularNatureofMatter,6E 129
"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
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olecular crystals can contain all of the listed
attraction forces e)cept: A@ =ipoledipole attractionsB@ (lectrostatic forces
C@ London forces=@ ydro'en %ondin'