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©AristoEducationalPressLtd.2010HKDSECHEMISTRY–AModernView(Chemistry)Coursebook3SuggestedanswersChapter25Simplemolecularsubstanceswithnon-octetstructuresandshapesofsimplemoleculesPageNumberClassPractice1ChapterExercise2Chapter26BondpolarityClassPractice4ChapterExercise5Chapter27IntermolecularforcesClassPractice7ChapterExercise9Chapter28StructuresandpropertiesofmolecularcrystalsClassPractice11ChapterExercise12PartExercise14Chapter29ChemicalcellsindailylifeClassPractice17ChapterExercise18Chapter30SimplechemicalcellsClassPractice21ChapterExercise22©AristoEducationalPressLtd.2010Chapter31RedoxreactionsClassPractice24ChapterExercise26Chapter32RedoxreactionsinchemicalcellsClassPractice29ChapterExercise30Chapter33ElectrolysisClassPractice32ChapterExercise33Chapter34ImportanceofredoxreactionsinmodernwaysoflivingClassPractice36ChapterExercise37PartExercise39Chapter35EnergychangesinchemicalreactionsClassPractice42ChapterExercise43Chapter36Standardenthalpychangeofcombustion,neutralization,solutionandformationClassPractice44ChapterExercise46Chapter37Hess’sLawClassPractice48ChapterExercise51PartExercise53HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.20101Chapter25Simplemolecularsubstanceswithnon-octetstructuresandshapesofsimplemoleculesClassPracticeA25.1(a)BCl3NCl3IF3(b)BCl3.Thecentralboronatomhasonlysixoutermostshellelectrons.IF3.Thecentraliodineatomhas10outermostshellelectrons.A25.2MoleculeNo.ofelectronpairsSpatialarrangementofelectronpairsNo.oflonepairsNo.ofbondpairsShapeCH44Tetrahedral04TetrahedralNH34Tetrahedral13TrigonalpyramidalH2O4Tetrahedral22V-shapedHKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.20102Chapter25Simplemolecularsubstanceswithnon-octetstructuresandshapesofsimplemoleculesChapterExercise1.eight2.eight3.six4.105.126.non-octet7.linear,180°8.trigonalplanar,120°9.tetrahedral,109.5°10.trigonalbipyramidal,90°,120°11.octahedral,90°12.2,213.1,314.shapes15.D16.B17.C18.A19.D20.A21.(a)A:;B:(b)A:WZ3B:YZ3(c)A.Thecentralatom(W)hasonlysixelectronsinitsoutermostshell.22.(a)X:TrigonalpyramidalY:Trigonalbipyramidal(b)107°(c)90°(forCl(axial)PCl(equatorial)bondangles)and120°(forClPClbondangleswithintheplaneoftriangle)23.(a)(b)HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.2010324.(a)SO2:SO3:(b)SO2:V-shapedSO3:Trigonalplanar(c)Sincetherearethreegroupsofelectronsaroundthecentralatoms(sulphur)inbothSO2andSO3,alltheO=S=Obondanglesareabout120°.HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.20104Chapter26BondpolarityClassPracticeA26.1(a)(b)(c)A26.2(a)NCl3hasthreepolarNClbondsandistrigonalpyramidalinshape.Asthereisaresultantdipolemomentarisingfromthethreepolarbonds,themoleculeispolar.BCl3hasthreepolarBClbondsandistrigonalplanarinshape.Asthedipolemomentsofthethreepolarbondscancelouteachother,themoleculeisnon-polar.(b)AstheorderofelectronegativityisFNBr,theresultantdipolemomentsofNBr3andNF3arepointingtodifferentdirections.Thesituationsareshownbelow:Inanon-uniformelectrostaticfield,thenitrogenendofNBr3willpointtothepositivepolewhilethenitrogenendofNF3willpointtothenegativepole.HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.20105Chapter26BondpolarityChapterExercise1.attract2.polar3.non-polar4.larger,less,smaller5.polar,cancelout6.polar,symmetrically7.deflection8.C9.B10.C11.B12.C13.A14.(a)Theelectronegativityvaluesofelementsdonotfollowthetrendofchangingmasses.(b)Itincreases.(c)Itdecreases.(d)2.5–3.5(e)0–2.8(f)CandF(g)ClandBr15.(a)(b)(c)16.(a)Y,Z,X.(b)(c)(d)17.(a)Mistakes:1.‘covalentbondinvolvingfluorineispolarinnature’2.‘allcompoundsoffluorinemustbepolar’(b)1.Thecovalentbondinafluorinemolecule(FF)isnon-polar.HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.201062.PolarXFbondsmaycancelouttheirindividualdipolemomentstogiveanon-polarmoleculee.g.CF4,SF6,etc.HKDSECHEMISTRYAModernView(Chemistry)Coursebook3©AristoEducationalPressLtd.20107Chapter27IntermolecularforcesClassPracticeA27.1(a)Whentheelectrondistributionaroundthetwoiodinenucleiisuneven,instantaneousdipoleisformedinwhichthesidewithmoreelectronswillcarryapartialnegativecharge.(b)A27.21.(a)Non-polarmolecules(b)Dispersionforces(c)(i)Thestatementiscorrectasbutanehasahigherboilingpointthanthatofpropane.Thestrengthofdispersionforcesincreaseswithincreasingmolecularsizeasthereisagreaterchanceofunevendistributionofelectronsinalargermolecule.(ii)Thestatementisincorrectasbutanehasahigherboilingpointthanthatof2-methylpropane.Butane(straight-chainhydrocarbon)hasalong,thinshape.Thiscontributestoalargercontactsurfaceareabetweenbutanemolecules,resultinginlargerdispersionforces.2.ClFandCH2Cl2arepolarinnatureandtheirmoleculesareattractedbybothdipole-dipoleforcesanddispersionforces.Ontheotherhand,F2andCl2arenon-polarinnatureandtheirmoleculesareattractedbydispersionforcesonly.Asaresult,ClFandCH2Cl2havehigherboilingpointsthanthoseofF2andCl2.SincethemolecularsizeofCH2Cl2islargerthanthatofClF,thedisp