Hwr Chong lnrlhuuoh

34 Tho d€viation of real gases from ideal behaviour may

pV / nRT

35 (a)

(a)

(b)

(b)

(c)

rj

ideal gas?iJc I Jcr 6fr r Joo,

l

6a!o. & Bondlns 2008

ltwa Cho.g ln3lliullon O!$r a Bondh! 2008

bo examined by plottingoV

- aoatnsl o as

nFlT -

. p, rtn

lf the above figure represents the deviations of the gases H2, 02 and COz at 40 'C,

(i) Match each gas to its corresponding curve (ie. X, Y or Z),

(10 Explain briefly your answers lo (a)(l).

lf the sem6 figure now repres€nts the devlations of a real ga3, A, at three temperatur€s,

(l) whioh curve, X, Y or Z, corresponds to the high€st temporaturo?

0l) Explain brietly your answers to (bxl).

RJC , JCI 8fl I lo0l

One sample of krypton consists of isotop€s with the following data;

Relatlve abundance (%l80 2.482

83 1.6

04 56.986 17.4

Calculate the relative atomic mas.s, A, of krypton from thgse dafa.

l/vhen sn evacuated glass b;b o[ 1,00 dmi capacity was filni wth the same sample ofkrypton at a pressure of 1,00 x 10" Pa and a temp of 300 K, lts mass incr€ased by 3.32 g.

Calculate the A, of this sample of krypton,

Ther€ is a difference in the values ln part (a) and pert (b), One reason is that krypton isnot an ideal gas. Suggest two reasons why krypton exhiblts loss ideal behaviour thanhelium und€r the sam6 conditions.

(d) Under what conditions of temp€rature and pressuro is krypton most likely to behave as an

ANSWERS

MULTIPLE CHOICE OUESTIONS

STRUCTURED AND FREE REPONSE OUESTIONS

I

lrl{ll NaFl lonic : 8Fr: slmolr @valont, r donates lonc pslr to empty orDltal ol B - datvo Dond

(rXll)

. >otuDt€ m n2v

. Conduct olsctrlcltyln aquoouQ atatg

r l{lahmnaalld

(bxD 'J[*l''/ [f,n(bx[) gasoous or liquld:

wcak VDWlorcoe

2 (.1

:F: H.a .t .l:F:B!N..H.. .l:F: H

w,r,t B: letrahedralw,r.t N: tetrahcdral

(bt

. lntrAmOlaOular H.DOndlng ln Z.ntl0pllOnol nol ln4-nitrophrnol.

. MolE cnaryy nscded to bruak lnlsrmolccular H-bondino in 4.nltoohenol o hioher b,p,

(cl

. Slts or, clouo bEger * vpwlorcct slrongor

. MO'O moloOulcs pgr unit volumQ * 3yrtrm morgcompect

r l.llnhrr M- al mlAa^l ^

mnahr{ t6 .lhr66l

3

(t)FHri Y9Wtoroog; NHt: H'Donoln9Enrr6u rMul.ad 6 ovrrcom. rkono lntsrmolecular H-bonds ln NHr *.hiohor b,o

00

. Mqlacular shapr dcErmha.l Dy no. ol Donq ptlto ano nnc palr3 arouno, mG o€nral .lomand nol thr.tot l numbcr of ,.

. Polri 0 bond palr0,0lona palrs ' trlgonal biPyramidal

. POCA:4 rcOlono of ghafcd c, 0 lono pairs * tstrghrdral.

I

(t) CN flD M,'52,0; CrN: (l[) 3Nlic-c:iNt

(lvl Lln.ar (v)

cyanogon: lormg H-oondt wlth othanol wlln lon6 palrs o,electrons on N * Bolublc in athanol

!!-O- a. ! t. a. L r, -O-

cH.cH"/ -H {xM: NEc-cEN ! *,." B' \CMH.

6

(|) Giant molecular atrucluro p Etroqg Sl-O bonda r oxltntlvo coval€nl bondlng betwrsnatoms ln ol.nt lhruadlmrnBlonal btruciurr.

(n)Giant ionlo strucluro - strong el€clrosiatic attractign betwcon oppositsly chargrd ion3.

Solld stata. lon8 only vlbratc about lix€d poaltions * no troe mobllg ions nor dclocalisad e.

(ilr) Glant melallic olsm6nt e largc aml. ot on€rgy roqulr€d to ovErcoms strong al3ctrogta$cattraction betwoon catlons and seE of delocallrod r.

Hwe Chone lhlliluti6n

HININIHft

'Y. rO'-N:N'T

ro:' b..

Ga!63 & Bondino 2008

Gr&t a Eondlng 2008Hw. chong lnatilution

6

(a)F2 and 12 non-polar + weak VoW forc€s exist botween the molecriles.Strength o, Vollt9rce6 dep€ndent on: no. of d * VDW between 12 etronser than F,,

(blNaF and CsC' ionic compounds; ions hcld slrongly by eloctrostatic forc6s,

-

Cs' and Cf hav€ larger ionic radii than Na" lnd F' € aflrEctiv€ torc€s botwBen theopposil€ly charoed lons are weaker tor CsCl.

(clshap6 0l molecul€3 dep€ndont on no, dl bond palrs and lon6 pairs oi iarouno centrat atornlFi : 4 bond pak6 and 2 lone palrs ot. around I e rquaro planar.BF4' : 4 bond pair3 and 0 lone palrs of c aound B 6 tetfahodrel,

.IOI NH!: H.bond,hfw[h wet6rmoleculcs $ v€ry soluble in wat€r.

" l. I H,Oand

togethor by relsuvoly strong H.bonds,. XrO iormj Z H-bonds per itoleculs on averago and NH-e torms one l{'bond on avorage

(b;iling point ol HzO i8 highsr than boiling point of NH3)'. More inercy .equirad to overcome H'bonds of H7O.

, I (b) L;,:l?[1i]tehishcstborrrnspornt'. slmplc molocular structure conaiatlng o, disffete covalently bondcd mol€cules held

. iltt::l[H#"ffi?;res ahd temporary lnducod dipor€s rBspoctivolv..

r mor€ onergy requirod to ovctcome permanent dipoles (but lasr than that required to

ov6rcomo H-bondlng)

.' Simple molecular Etructuro con8lgting ot di8cret6 covalently bond.d molocule! held

. b.o of HCI ls

7

(a)

jx.i

;t:' :i:llnear

ii;r; :IIJFi""'r*squaro planar

(b,

m.p alEO dapand.nt on how close th€ molecules canpack log€ther ln the Bolld slete.XaFr: lin€at - moleculsr approach moro closely thansguarc planarX€F4 :

l.M.F between XeF2 mol.cules hloh6r $ hloher m,D.

(cXl!

Noble gasos hevc all pglrcd olectttns. To r6act to tormcovalent compounds, ths nobl6 gase8 needed to promotoeleclrons up to€ 6mpty orbitals ot higher energy 80 thatsingl€ electrons,ar€ pr€genl,Largo amount ol energy is nsodsd to promot€ th6 lselectrons in h€lium to the next hlgh€r €nergy emptyorbital (2s) 30 that holium do€8 not r€act with fluorine,Howcver, less energy ls needed to promolo th6 5pcleclron in x€non to th6 ompty orbltal so that lt ls posslblefor Xe t6 r€ecl wlth F

(cxuThe energy needed to promoto el€c'lrons lo orbital8 of a higher oncrgy tev-t ls cornpensateoby the ncw bonds that ere tormed. Slncc strength o, covat6nl bond ii dependent onditlorsnae in electronegaUvity and fluorins being very €l€clrohegative, Xe-F bond is muohstronger then Xe-l bond.

10

(a)(ll

No of Clectrons: HF < CHrC/ < CHrl < CClr'H"nce r"n der wbals,forcer (of thr instantanBous dipole'induced diPole tyPe): HF < CHsC,

< CHrl < CCIHowcver, nyamgen bonding botwcsn HF moleculos caurqs lts boiling point to be hlghcr

th'nexDect.d.ienca.boilinooolnt:cH!c,<HF<CHrl.CQ/r-

(aXll)

dipol! momanl,D

0CHJ CHrCI

(aXlll)

CClr ls non-polar moleculo honcs lt has zoro dipolo

moment. Allhoueh tha C-C, bond ls Polar, CC,. has a

regular tctEhedral thapr, 30 all lt3 dlpol. momentt.oa-ncel each olher out,,rcsulting In ovorall zero net dipolemomont.CHrC/ and CHll have (non-zsro) nel dlpolo moments. C,

ie more oloctronogatlve than l, hcnce th€ C-CI bond is

more polar than thc C-l bond, thu3 tho dlpole moment ot

CHrCI > CHrl.

(bxD

[;[:'+l;]'(bl(il) ,{),r'

8

(al

Nacl ls a giant ionic compound while CCI{ is I simple molecuiar -mpounO. TnG Ouffiboiling of NaC/, strong ionic bonds are broken between th6 Na'and Cf lons,.whoreas inCCla, boiling involves br€eking lnt€rmol€cular torcos ol attlacton thus the VOW lorcos otettraction betwe€n th€ ccla molecules are broken and not th6 strong covalent bondsbotween the C and H atoms.Both ionli and covalent bonds ar€ stiono bond3.VoW forces w€aker than ionlc bonds € moro en€rEy is n€aded a NaCl laroor b.o

(b)

VSEPR statcr that the €l€ctron .pah8 will b. plac.d ,uahecltwii-Irom each othor iAminimizo rEpulsion and maximize stebllity, Lone pair.lono pelr repuleion is stronger thanlon6 pair.bond.palr reputslon which ln turn i3 ltrong€r than bond pali-Oond pair repulilon,AIHa-: 4 bond"pairs and O lone pairs e ietrahedrai.

lone palr around eachTrigonal pyrbmidal around'each N 'Bond angle H-N-H q 1071

3 bond pair3 and 0 lone pairarcund Each NTrigonal planar around each NBond

Hwe Chong lnllltutlon G!li! E Bonding 2008

Hw! Cho^g lnslilulion O$.s A Bondlno 2006

1t

(a)

ArF!: ionic compound - giant lattice with stronoelectrostatic atlmcilon betwecn Af' and F'lon3.Largo amount ot encrgy nceded to overcomi 3ttongtorcBs of attraction - hlgh m.p.ArCh: simpl6 coval€nl mol€culo r lveak VOWtorceaSmall amount ol Gn6rgy n66d6d to.overcom6 thewoak intermolecular forces,

(bN0

l-::*lf;ir;; f,,'l'

L'u"'t: lSquar€ danaf

(bxlDLrquld EtFi autolonisos to giv€ mobil€ lons, accountingtor its Electrical conductivity,

2BrFr = BrF,'+ BrF,-14

(aXl) He<Nz<COz

(aXll)

All the gasBs experience temporary dlpole-temporarydlpole i induced dipole-induced dipole / dispersionlorces , VDW intersctions betw6sn molacules both in

(bxr)

[:rry:]

thc liquid and ga8eous $tat38.

CO2 vsn dor Waals' hteractions arc the strongesl as

h has the mosl numbor of slectrons, follo\f,ed by N2

and then He which has the leasi numbel of alectlons,The atronger h€ intermolecular lntsractions, thecaslor it is for tho molecule8 to over@me the KE in

ih6 random oaBBous statc.

(b)0[

";-EI'-tg gquare planar becaulo it has 2lonc pairt and 4 bond parrs'. Aciomfnd.to VSepn Thcory, electron pahs around the contral atom ln a molqcule

arrange tf,cmaelvcc go ag to minlmltr €lectron Pair€lectron pair repulglon'. t.o - l.i reoulslon > l.o. b.o repulslon > b.p - b.p Ispulslo4 =--''-

(c)

3Fr

12

(rl

El€ctron pairs about the central atom aranoe_tham3€lw8 aE far aparl a3 possibl€ so asto minimizo inlarelectronic repulsion snd marimlzo cteblliv,Th€ axlent of lnt€relecronlo EpulBion la as follows: lone palr.lone pair repuhion > lonepair.bond pair rapulslon > bond p6h.bond pair repul3lonA multiole bond ls tEatod a3 a si^ole bond-

(bt

Nn!: i IoDe Palr, ., DOnq PalrsNn2-: 2 tonapairs,2 boni pairu around NNHr': 0 lone pairs, 4 bond palr! eround NSince lone pail of €l€ctrons exer{! lho gt elcll cxtent o, r€pulslon, thc bond angledocreases with the lncrease ln number o, lon€ p8irc. HBncr, lh€ odef o, lncreaslngH-N-H bond anole ls NH,- < NH' < NH;.

(cl

I he intramolocular bonds in Doth €thyl€n€ glycol and acetono a.6 covalent bonds.Tho intErmolecular bonds in othyl€no glycol are hydrog€n bonds while thet tound inacolone 6te VOW rorc68.As intcrmolecular hydrogen bonds ere slrcnoer than VoW forcee, more energy isnaeded to over.come the lntcrmolecular forcos ol aftractlon betw€en ethyl€no glycolmolacules than aceton€ molaculor during boiling. TherefoF, €thyleno glycol ha3 ahigher bolllnO point !hd hence ls lars volatile.Wrarl the intermolecular forc€s ol etrectlon ars gtrong, tho indlvldual molecules los6thek mobility, i.e. ebllity lo mov6 tr6ely, Sinc€ ethylonr glycol poseesses intermolecularforces ol atlraclion lhan acclone. lt hes r hldhat visd63itv.

t3

(aXl)

To form PrP, porbltal3 of P n€€d to ovedap side.on toform two n-bonds. Since P ie a relatively big etom withdit u3e orbital3, glda.on ovedap o, its porbitelg lr muchless effsctiv€ than head.on ov6dep to lorm $bonds.Thus. P do€B nol occur neturallv ac PrP molecule3.

(bxt)

[,bi ., l-| :N:or I

L'o.;' "

l

[,;i#]'

(axlD

Eoilang involv6s overcomino int€rmolecular lorce6, notcovalonl bonds within tho moleculo.Both N2 end Pa are non.polar, so that instsntaneousdlpole.lnd'Jced dlpolo interections occur bstwcen th€lrmolecules.Aa Pr hag a graater numbcr of €l€clronr, lnstantaneousdipole.induced dipola inleractions are stDng€r betweenP1 moleculos, ra3ulting in high€r bolllng point lnohogohorus.

(b,([]

To lorm NO{-, N must b6 abl6 to accommodate 106lectrons in lts valence shell. Sinco N ii ln perlod 2, it hasno low.lying 6mpty d orbitals to €rpand its oct6tandhcnc€ cannot accommodete more than eight €leclrons inits velenco shell.

15

(rl

5e[[tr.fohr il.C l bondl anrnged in a dlrtortod trtrahedral-/ acs'8aw !htp.' mc Dond

Atpotc momcntr Oo not c.nqel oui vcctorlally / honc. h!!.nct dlPol€ momont whrlcar CCr.

hsr polar c-c, bondo but a totr.hodral rhape ln whlch lhe bond dlpole momlnle cancel out

vcctorlally I hc4co no nct dlpolc momrnt, Hence, SClr has an ovcrall not dipol. momcntwhllr ll(1,. hrilam hat dl6ol. momanl.

(bxll

EoiF66ffinoi and wAailorma hydrogen bonding with mol6cul6s ot ltE own. Howevor'

,"ini'noiiormcon avaago, t hyirogin bondlng per molccule. while H2d forms 2 hydrogon

bonds Dor molocule, Henie, waiar hag two times moru 6xtensivs hydogcn bonding and

thur, niors cnergy 18 toqulrcd ovgrcomc those Sttongar atlractlons in wator' Thcrefors wirter

(bxlll

ffiii-pcnlonlorcel.H9wry.e1CHrCllzCl,lrCHaNl{lha9non.potir otratn wntd har r morc clongaicd clcctron cloud, whlch ha! gfrtler rudao arca of

toniact for dlrperelon forcer to bc ilt up, th.n lhe hlghly.branchcd HN(CaHrh. Hcnc. the

dlrprnion lorceg ln HN(CzHs)rwlll b. ltrongar than that lor CHTCHTCHzCHzNHz ,

a6htrlbutlnd t6 thi hlohsr bolllno oolni.

(sXll

o-bond (hra&qn overlaP): Cf) or

,r'bond (slCa€n ovorlaP): W

(c)(lll

FIh-TfE:ef6as e gtronocr bond bscause firstly, it ha! a shorter bond lcngth/8m8ller atom

than thc H-Br. hcnce a morc efloctlve ovodap of olbitals.Prlr 2r

crc bond ls a doublc bond, lncreaE€ ln no. ol bonds/no, of Bloctrons in lhc bond ehortens

thr bond and lncrearcl bond rtr€ngih,CrC bond conrl3ts ol ons slgma and one pi bpnd, whllc C-C ie a sigma bond.

Sincc, pl bond lg weakor than a sigma bond, hence thc bond enorgy ot thc C=C doublo

bond it lrsr than twice ths bond tnergy ol C-C slnglc bond.

Hwa Chong lnllitulion

t'tIr

Ga!€! & Bonding 2009Hw. Chong lntlilllio^ G.rrt & Bondin0 2000

16

(al

N2<CQcHF<NeF<MggN2: induced dlpole.lnduced dlpolc inlelactlon w6aker than p6rmanenl dipole-permanmentdipole in CO. HF cxhibits hydrog€n bonding, much stronger than pd.pd in CO.NaF E MgO ar€ both.ionlo compounds with strono €l€ctrobtatic attractive (orcas, MgO has ahioh6r latlica anthalov du€ to smallsr cation end hiohef chrto€.

(bxt)hI I N:H

:o:H

(bxfl)N: ofly 1 lone Parf ot er€dron8O: 2 lon6 pairs of elcctrons. ,

lon6 Dair r€oulsion > bond oalr reDUlslon

{bxill N is less electronegatlvo than O

,l?

(eXl)xx

roxx

xx

otlc/xta

(aXll) 4 regions ol elecron dcnglty, 1 lone pair and 1 unpairedelactron € b€nt shapg

oolar molecule. can lorm favoureble H-bonds with water 4 3oluble in wat€r

(a)(lv) Slee ot electron d0ucl ol 8192 is lafggl than GI92, m0re ea8ily polarlZ€d, Strengm ot pd-pd iS

stronoer € m6ra en€adv teouirad e hloh€r mellino ooini

23

(a) 8F3 ha3 3[Irplt mplocular structur€ wlth wcak dispersbn lorcas of anraclion betw€on thoBF. molecules.

(btEoth NaF.and MgF2 hava glant lonlc lattic€ structura, the higher tho lattlce €nergy, thghighrr thc mcltlng poinl. The cha0os on NaF are (+1) an4(-1), whiie tor MgFr, aro (+2) and(-1) rdsoecllvelv: The eum ot lonlc radll ol Mot' and F-is smallgr then thetol Na'and Fanv I > 1241'C

l8

(aXl)Tru6. Eloctronegativo specios pull8 €teclrons Irom.hydro06n cauring a 0 and 0 cnergos

Fals€. souarB olaner thaoc. olDolo mom€ntr canccl €ach oth€t out. Not oolarFalse. Mg"- atrd O" heve highor charge donsity then Na' and Cf, qfonger slectro3taticattraction. More enemv roouired - hiohor m.o;

(b) 4-hydroxyb€nzoic acid. No lntra-molGcular H.bond b€twaen -OH & -COOH, can torm moreextenslve H.bondino wlth HrO, MorB favourablo lnteracllonr - molo soluble

(cll2: Bimplo diatomic molBcul€s: Dietnond: giant covalent 3tructur6, l2l weak V0W lorces;oiamond; etrong C-C covalont bonds. More €ncrgy r€qulr€d to overcome covalont bondsthan VDW torce3 l, has lower b-o * mor€ volatll6.

24

(a)

Prs3enc€ of polar group -cooH, psrtlally hydrolysed in wstor in the body of 8yslsm, fofmlon.dlpolo lntoractionr / hydrogBn bonding with wat6r, honc€ travel ta8t in tho body systBm,Preccnca oi bcnzene rlng, ihc hydrophobic / non-polar naturB results ln tho 3olubility in tho,.llv .^mMlid.

(bl IilOOnal olanar. 120'8nd v.shaoad 105'(cllll Firrt glt€rnativ€ with rcmoval of acidio oloup -COOH.

(cl(ll)

1'' druo: Molthg polnl l$ low6rBd. as dipolo-dipole attraclion is woaker than H.bonding.Solubillty of moleculor ls lowsr€d a8 hydlogen bonding / ion.dipolo att.actlon is no longerp03slbl€.2io drug: \Mth the decroate in polarity ot the moleculo. both maltlng poinl and solubllity ar6exoccted io be l6wer.

(d)AEpmn und€reoss alkalho hydrolysls to produo€ lons Na -o-c0H{-cotNa' and oHrcoo-Na'. Meltlng polnt wlll lncrcase due to proEence of slrong ionlc bonds, Eloctrical conductivityls ot(occtad io lncreerc wllh lncr.alc ln no- of lons.

10

(rl CH3CH2CI{(OH)CH!: H-bonding butwith 6i€ric hlndrance. less 6xtonBlve H-bondingCH!(CH2)rCl; pd.pd lntcraction, w€akcr than H.bondingCH"/Cl.l.)"CHr VDW forces. smeller el.elmn cl6ud than ab6v. c6mn6und

(bxl) E3[; i'ili"lill*Tl#:'li;,XJ:onarpvramrd, ",;i-,'*lfrl'(bxt0 PCr! lar0er electfirn cloud, more eaBily polariseble, ltrongar VDW torcoB, more energy

requirod to overcome + hioher b.o.

28

(l) Sct Qg(Q) 0u

Ethenei sp'; Hydrszing : sp'Hybrid orblials ol ethone:

(ulHydrazlnr_ha8 a highor bolllng point than €thens, Moro onergy is ne€dod to ovsrcom€ lh6etrongor hydroggn bondlng b€tw.on hydrazln€ molcculcs than tho woak€r van dcr Waals'forcg3 belwaen ethena mol6cula3.

20

(rl As bond lenoth increaseB- bond enemv decaaa363

(b)It has thc short€sl bond l€ngth among helogen3 y€t haq how bond an6tgy. shon bondl€noth € strono r€oulslon b6twe6n lon6 Dair! of clectrons bh F 6tohs.

(c)Groet EN ditf€roncc b/w H and F r uncqual dhtrlbutlon of 6l6ctron cloud / polar, Atlractionb/w th6 partially charged H & F / Covelont moleculas with lonlc character $ lncreaea energyrcoillred lo br.al bond

2A

(rlo .^lg:0,''.Y'; " '

b.at

I

(aXl0f i:' +, i:,1

L ti='r :i:: l

(lrXl! '12

(bxil) n r 1: OX nO. u +4

(c) U()ti tlmPlC moleculalt Weak van dCr WaAlS'torcsgTcOr: olant molccula?. Bln no covalont bondo21

(aXl) BE ol NrN bond 18 small than that of cro bond. c and Q hes v6ry dltforent EN, hence thebond ls oolarwhile the NrN bond E non-polar

(.Xll) co ha8 a higher boillng point than N2. P{l-pd anlactlon3 between polal co molecul€s areatr

^d.r thah th. \rn\tr t^r..e h.tu..h na^-6alrr N- m^l.Arlee

(bxl) OII N :OI (bxil)

+O:N-O

Noa'llinoart

o.-J-o-NOi

(b00

27

(lt EF3 ha3 3 bonU pairs and 0 lona palts around central stom B hencc trigonal planarPF. hes 3 b6nd 6elrB end I l6ne Daheround c.nlEl alom p hen.. lridonrl ovDml.lrl

flil Hvdrooan bonds 6xist belweEn 2 HF molacul€s. and HF Exists as dimers.

(m)tsoln Bomert nava sam€ Srmple mplecular 6tructuro and weak tnlormol€culat vDW forc€6 oIsttraction, thur rlmilar boiling polntlr. C/s lsomor cannot pack into a crystal as oasily ss thetmns lsom6t thu. low.r msltino 60lnl-

IHwe Chono httitlllon G6!e3 a Bondh! 2006

;iviT is not a constant Lr diff€ront volumo and temp al constrant

High P, moleculeg are packod clos€ly tog€ther - repulsion, gas lesS comprcssibls e

. larser;ifilc=ire, eieclron cloud, more polari3able , strongor and mora

. laraer size. occuov laroot and morc Sionlficentvolumo than He

28

(a)

Cl lo0.so t c

'"Jffi'*'" (bxu,:c.r; i 10i:

:il :i;:'kidonel bio$emldal

(b)(il) tPc,ol-

(bxm, Molea,lat forrn. cc-r. is no6-polar and dannot Solvate ion3 €floctively, Thus Pcrs exist a3 the

non-Dolar molecular lorm which interacts most lavourably with CC4,

29

(.1LiF: lonic compound strong €l€ctrostatic anraction botwoBn Li and F-.

HF: Stron0 hydrogen-bonding betwoen moloculeS.NF.r w.rk 6d-od interaction b6tw6en mol€cul63.

(blEcan expa;a;aGifec€we af tho availabllity of low'lying 6mpty 3d orbitels

N cannoi expand oct€t as there are no cnergeticqlly acc€saible orbitals to accommodate the

(cxl)

bh al{

I^[F iai. F

clt

,r .F'ffi.?tN

lrsi

(cXll)

dipolo moment in lrans lsomar cancsl eech other. /lansisomct lt not polar and 13 held togoihor by weak VDWtorca3pd.pd lnteractlon in cds lgomer ls Etronger than VDWforc€3 ln ,rens isom€fmoro en6rgy 16 tequlred to ovcrcomo pd'pd interactionln ois lsomcr ihan VOW forcel ln lrans l3om6rcauElno cis lsomer to havc a slighuy high€r b'p than,Hrs l36met

30

(rl ffipplng of orbltal3. r bond i! rormod trom tho side-onoverlaDolno ol GorbltalS.

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