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ACEGENERALCHEMISTRYIANDII(THEEASYGUIDETOACEGENERALCHEMISTRYIANDII)BY:DR.
HOLDENHEMSWORTH
Copyright©2015byHoldenHemsworthAllrightsreserved.Nopartofthispublicationmaybereproduced,distributed,ortransmittedinanyformorbyanymeans,includingphotocopying,recording,orotherelectronicormechanicalmethods,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembodiedincriticalreviewsandcertainothernoncommercialusespermittedby
copyrightlaw.
DISCLAIMER
Chemistry,likeanyfieldofscience,iscontinuouslychangingandnewinformationcontinuestobediscovered.Theauthorandpublisherhavereviewedallinformationinthisbookwithresourcesbelievedtobereliableandaccurateandhavemadeeveryefforttoprovideinformationthatisuptodateandcorrectatthetimeofpublication.Despiteourbesteffortswecannotguaranteethattheinformationcontainedhereiniscompleteorfullyaccurateduetothepossibilityofthediscoveryofcontradictoryinformationinthefutureandanyhumanerroronpartoftheauthor,publisher,andanyotherpartyinvolvedintheproductionofthiswork.Theauthor,publisher,andallotherpartiesinvolvedinthisworkdisclaimallresponsibilityfromanyerrorscontainedwithinthisworkandfromanyresultsthatarisefromtheuseofthisinformation.Readersareencouragedtocheckallinformationinthisbookwithinstitutionalguidelines,othersources,anduptodateinformation.
Theinformationcontainedinthisbookisprovidedforgeneralinformationpurposesonlyanddoesnotconstitutemedical,legalorotherprofessionaladviceonanysubjectmatter.Theinformationauthororpublisherofthisbookdoesnotacceptanyresponsibilityforanylosswhichmayarisefromrelianceoninformationcontainedwithinthisbookoronanyassociatedwebsitesorblogs.
WHYICREATEDTHISSTUDYGUIDE
Inthisbook,ItrytobreakdownthecontentcoveredinthetypicaltwosemesterGeneralChemistrycourseincollegeforeasyunderstandingandtopointoutthemostimportantsubjectmatterthatstudentsarelikelytoencounter.Thisbookismeanttobeasupplementalresourcetolecturenotesandtextbookstoboostyourlearningandgohandinhandwithyourstudying!
IamcommittedtoprovidingmyreaderswithbooksthatcontainconciseandaccurateinformationandIamcommittedtoprovidingthemtremendousvaluefortheirtimeandmoney.
Bestregards,
Dr.HoldenHemsworth
Yourreviewsgreatlyhelpreachmorestudents.Ifyoufindthisbookhelpful,pleaseclickbelowtoleaveareviewonAmazonortosharethebookon
Facebook.Nothinghelpsmorethanafewkindwords.
TABLEOFCONTENTS
CHAPTER1:IntroductiontoChemistry
CHAPTER2:ComponentsofMatter
CHAPTER3:StoichiometryofFormulasandEquations
CHAPTER4:ChemicalReactions
CHAPTER5:QuantumTheoryandAtomicStructure
CHAPTER6:ElectronConfigurationandPeriodicProperties
CHAPTER7:ChemicalBonding
CHAPTER8:GeometryofMolecules
CHAPTER9:BondingTheories
CHAPTER10:GasesandGasLaws
CHAPTER11:Thermochemistry
CHAPTER12:Solutions
CHAPTER13:ChemicalKinetics
CHAPTER14:ChemicalEquilibrium
CHAPTER15:AcidBaseEquilibrium
CHAPTER16:SolubilityEquilibrium
CHAPTER17:Electrochemistry
CHAPTER18:NuclearChemistry
CHAPTER1–INTRODUCTIONTOCHEMISTRY
WhatisChemistry?
Chemistryisthebranchofscienceconcernedwiththeunderstandingofmatter;thesubstancesitiscomposedofandtheirproperties,aswellasthewaysinwhichtheyinteractandchangetoformnewsubstances.
Matter
Matterisanythingthathasmassandtakesupspace.Massistheamountofmatteranobjectcontains;awayofquantifyingmatter.Matterexistsinthreephysicalstates.
Solid–matterwithfixedshapeandvolume(rigid)
Liquid–matterwithafixedvolumebutindefiniteshape
Takesontheshapeofthecontaineritisin
Gas–matterwithoutafixedshapeorvolume
Conformstothevolumeandshapeofitscontainer
PhysicalandChemicalProperties
Physicalproperty–characteristicsthatcanbemeasuredandobservedwithoutchangingthechemicalmakeupofthesubstance
Examples:color,meltingpoint,boilingpoint,density,etc.
Physicalchange–asubstancechangesitsphysicalappearancebutdoesnotchangeidentity
Changesinstate(e.g.,liquidtogas,solidtoliquid)areallphysicalchanges
Chemicalproperty–anypropertythatbecomesevidentduringachemicalreaction
Examples:pH,corrosiveness,etc.
Chemicalchange(akachemicalreactions)–asubstanceistransformedintoachemicallydifferentsubstance
Mixtures
Mixturesarecombinationsoftwoormoresubstancesinwhicheachsubstancekeepsitschemicalidentity.Mixturescanbeseparatedintotwoormoresubstances.
Heterogenousmixtures–mixturethatisdividedintodifferentregionsofappearanceandproperties
Resultsfromcomponentsnotbeingdistributeduniformly
Homogenousmixtures–mixturethatisuniformthroughoutwithoutanyvisibleseparations
Solutionsarehomogenousmixtures
Whereasolid(thesolute)isdissolvedinaliquid(thesolvent)
ElementsandCompounds
Puresubstanceshavedefiniteandconsistentcompositionandarecomposedofelementsorcompounds.
Element-substancethatcan’tbebrokendownintoothersubstancesbychemicalmeans
Compound–substanceformedfromtwoormorechemicalelementsthatarechemicallybondedtogether
Lawofdefiniteproportions
Purecompoundsalwayscontainexactlythesameproportionsofelementsbymass
Energy
Energyisthecapacitytodowok.
Kineticenergy–energypossessedbyanobjectduetoitsmotion
Potentialenergy–energystoredinmatterbecauseofitspositionorlocation
Somethingsuspendedintheairhashigherpotentialenergythansomethingsittingontheground
TotalEnergy=potentialenergy+kineticenergy
Lowerenergystatesaremorestableinnature
Lawofconservationofenergy
Energycan’tbecreatedordestroyed…butitcanbetransformed
Example:potentialenergycanbeconvertedtokineticenergy
Energyisalwaysconserved
ScientificMethod
Thescientificmethodisatechniqueforinvestigationthatisusedtoanswerscientificquestions.
Hypothesis-aproposedexplanationmadeonobservationsorlimitedevidencethatservesasthestartingpointforfurtherinvestigation
Theory–explanationofgeneralprinciplesofaphenomenathathasbeenrepeatedlytestedandobserved
Fact–indisputabletruth
Stepsinscientificapproach
Observations,Hypothesis,Experiment,Developmentofamodelortheory,Furtherexperimentation
MeasurementsMeasuredquantitiesconsistofanumberandaunit.
UnitsarestandardizedintheformoftheInternationalSystemcalledSIunitsUnitshaveassociatedprefixestomakethemeasiertouseandreports
Conversionfactors–amathematicalmultiplierusedtoconvertaquantityexpressedinonesetofunitsintoanequivalentquantityexpressedin
Example:1yard=3feet(10yard=30feet)ScientificNotation
ScientificnotationisawayofhandlingverylargeorverysmallnumbersScientificnotationforanumberonlycontainssignificantfigures
Examples525,000=5.25x105
2,301,000,000=2.301x109
0.000000000670=6.70x10-10
Considerthefollowing:0.000023=2.3x10-5
Theexponenton10isthenumberofplacesthedecimalpointmustbeshiftedtogivethenumberinitslongform
Positiveexponent,shiftthedecimalpointtotherightNegativeexponent,shiftthedecimalpointtothe
leftSignificantFigures
Allnon-zeronumbersarealwayssignificant
1,2,3,4,5,6,7,8,and9Zeroesinbetweennon-zeronumbersarealwayssignificant
10001–5sigfigsAfinalzeroortrailingzeroesinthedecimalportionaresignificant
0.00500–3sigfigs1255.0–5sigfigs
Allzeroestotheleftofadecimalpointandthataddvaluetoanumberaresignificant
100.0–4sigfigs0.1–1sigfig
Inthiscase,thezeroaddsnovalue;itistheretoavoidconfusionandbyconvention
ExactNumber
Exactnumbersareconsideredtohaveaninfinitenumberofsignificantfigures
TheydonotaffectaccuracyorprecisionofanexpressiontheyareinYoudonothavetoconsiderthesignificantfiguresinexactnumberswhendoingcalculations
Conversionfactorsareexactnumbers
1yard=3feet(thereareexactly3feetinayard)1foot=12inches(thereareexactly12inchesinafoot)
MultiplicationandDivisionSignificantFigures
Firstperformalloperationsandarriveatananswer
Theanswershouldhavethesamenumberofsignificantfiguresasthenumberwiththeleastamountofsignificantfiguresusedinthecalculations
AdditionandSubtractionSignificantFigures
FirstperformalloperationsandarriveatananswerInadditionandsubtractionyouonlyhavetoconsiderthesignificantfiguresinthedecimalportion
Theanswershouldcontainnomoredecimalplacesthanthenumberwiththeleastamountofdigitsinthedecimalportion
Multiplication/DivisionCombinedwithAddition/Subtraction
FolloworderofoperationsIfthenextoperationtobeperformedisinthesamegroupasthepreviousoperationthendon’troundthecalculation
Forexamplewhenyouperformdivisionandthenmultiplication,youwouldnotroundthecalculation
Ifthenextoperationtobeperformedisintheothergroupfromthepreviousoperationthenyouwouldroundtheanswerusingtherulesbeforemovingontothenextoperation
Example:Youperformdivisionandthenextoperationissubtraction
Youwouldfirstroundtheresultofthedivisionusingthesignificantfigurerulesfordivisionbeforeyouperformsubtraction
AccuracyandPrecision
Accuracy–howclosearesultistotherealvalue
Precision–howcloserepeatedmeasurementsareinrelationtooneanother
Accuracyvs.Precision:
Uncertainty
Uncertainty–errorinameasurementExpressedasastandarddeviation
Whenmakingameasurementinvolvinganinstrument,themeasurementismadewithoneuncertaindigit
Example:Youmightrecordthemeasurementas20.03The3isanuncertaindigitbecauseitisestimatedandcan’tbereadoffexactlyfromtheinstrument
Temperature
Temperatureiscommonlyquantifiedusingthethreeunits:kelvin,Celsius,andFahrenheit.
Kelvin(K)–“absolutetemperaturescale”
Startsatabsolutezero
Containsonlypositivevalues
Celsius(˚C)–“waterbasedscale”
0˚C–freezingpointofwater
100˚C–boilingpointofwater
Mostcommonlyusedscalearoundtheworld
Fahrenheit(˚F)–“mercurybasedscale”
CommonlyusedintheUS
ConvertingTemperatures
FormulaforKelvintoFahrenheit:(9/5)(K-273)+32
FormulaforKelvintoCelsius:K–273
FormulaforCelsiustoKelvin:˚C+273
FormulaforCelsiustoFahrenheit:˚Cx(9/5)+32
FormulaforFahrenheittoKelvin:(5/9)(˚F–32)+273
FormulaforFahrenheittoCelsius:(5/9)(˚F-32)
CHAPTER2–COMPONENTSOFMATTER
ComponentsofMatter(Definitions)
Element-substancethatcan’tbebrokendownintoothersubstancesbychemicalmeans
Molecule-acombinationoftwoormoreatoms
Compound–substanceformedfromtwoormorechemicalelementsthatarechemicallybondedtogether
Mixture-twoormoreelements(orcompounds)minglingwithoutanychemicalbonding
LawsofMatter
LawofMassConservation
Totalmassesofsubstancesinvolvedinachemicalreactiondonotchange
Numberofsubstancesandtheirpropertiescanchange
LawofDefiniteProportions:
Purecompoundscontainexactlythesameproportionsofelementsbymass
LawofMultipleProportions
Iftwoelementsreacttoformmorethanonecompound,thentheratiosofthemassesofthesecondelementwhichcombinewithafixedmassofthefirstelementwillbeinratiosofsmallwholenumbers
PostulatesofDalton’sAtomicTheory
Allmatterconsistsofextremelysmallparticlescalledatoms
Allatomsofanelementareidentical
Theyaredifferentfromatomsofanyotherelement
Includinginmassandotherproperties
Atomsofanelementcan’tbeconvertedintoatomsofanotherelement
Compoundsresultwhenatomsofmorethanoneelementcombine
Agivencompoundhasaspecificratioofatomsofdifferentelements
PeriodicTableofElements
Theperiodictableisanarrangementofelementsinrowsandcolumnsbasedontheiratomicnumber,electronconfigurations,andchemicalproperties.
Period–horizontalrowonthetable
Group(Family)–columnonthetable
Elementsontheperiodictablecanbeclassifiedasmetals,nonmetals,andmetalloids
Metal–substancesthathaveluster,highheatconductivity,highelectricalconductivity,andaresolidatroomtemperature(exception:mercury)
Nonmetal–substancewithoutanymetalcharacteristics
Metalloid–substancethathavebothmetalandnonmetalcharacteristics
Atoms
Anatomisthesmallestunitofmatter.Atomsinteracttoformmolecules.Atomsarecomposedofsubatomicparticles(electrons,protons,andneutrons).
Electrons–negativelychargedparticles
Carriesachargeof-1.602x10-19Coulombs(C)
Chargeofatomicandsubatomicparticlesaretypicallydescribedasamultipleofthisvalue
So,referredtoas-1
Mass=9.10938291x10-31kg
Protons–positivelychargedparticles
Carriesachargeof+1.602x10-19Coulombs(C)
Referredtoasa+1electroncharge
Mass=1.67262178x10-27kg
Neutrons–unchargedparticles
Electricallyneutral
Mass=1.674927351x10-27kg
Protonsandneutronsarefoundinthenucleus
Nucleusisthecentralcoreofanatom
Electronsorbitthenucleusinan“electroncloud”
Elemental(atomic)symbol:shorthandrepresentationofatomsofdifferentelements
ExampleofanElementonthePeriodicTable:
Atomicnumber-numberofprotonsinanatomofaparticularelement
Foraneutralatom,numberofelectrons=numberofprotons
Allatomsofanelementhavethesameatomicnumber(samenumberofprotons)
Massnumber=thenumberofprotons+thenumberofneutrons
Allatomsofanelementsdon’thavethesamenumberofneutrons
Atomicweight(relativeatomicmass)–averagemassofatomsofanelement
Calculatedbasedontherelativeabundanceofisotopesinthatparticularelement
Units:atomicmassunits(amu)
Isotopes–atomsofanelementwiththesamenumberofprotonsbutwithadifferentnumberofneutrons
Sameatomicmassbutdifferentmassnumber
TypesofChemicalFormulas
Chemicalformulasareawayofexpressinginformationabouttheproportionsofatomsthatconstituteacompoundusing:elementsymbols,numericalsubscripts,andothersymbols(e.g.,parentheses,dashes).
Empiricalformula–smallestwholenumberratioofnumbersoftheatomsinamolecule
Molecularformula–actualnumberofatomsinamolecule
Structuralformula–chemicalformulashowinghowatomsarebondedtogetherinamolecule
CovalentandIonicBondsCovalentBonds
Twoatomssharetheirvalenceelectrons(electronsintheoutershellofanatom)
TwoTypes
Non-polarcovalentbond–electronssharedequallybetweenatoms
Electronegativityofthetwoatomsisaboutthesame
Typicallyelectronegativitydifferencebetweenthetwoatomshastobelessthan0.5fornon-polarbonds
Electronegativity–anatom’sabilitytoattractandholdontoelectrons,representedbyanumber
Polarcovalentbonds–electronsshareddisproportionatelybetweenatoms
Electronegativitybetweenthetwoatomsisdifferentbyagreaterdegreethan0.5butlessthan2.0
IonicBonds
Electronsaretransferred,notsharedbetweenatoms
Anatomwithhighelectronegativitywilltakeanelectronfromanatomwithlowelectronegativity
Typically,differenceinelectronegativityismorethan2.0
Ions
Ionsarechargedatomsormolecules.Ionsareformedwhenatomsorgroupsofatomsgainorlosevalenceelectrons.
Monatomicion–singleatomwithmoreorlesselectronsthanthenumberofelectronsintheatom’sneutralstate
Polyatomicions–groupofatomswithexcessordeficientnumberofelectrons
Anion–negativelychargedion
Cation–positivelychargedion
Ioniccompounds–associationofacationandananion
Thecationisalwaysnamedfirst
NomenclatureRulesforChargesonMonoatomicIons
Elementsingroup1formmonoatomicionswithchargesequaltotheirgroupnumber
Naisagrouponeelement,formsNa+,+1charge
Elementsingroup2formmonoatomicionswithchargesequaltotheirgroupnumber
Mgisagrouptwoelement,formsMg2+,+2charge
Elementsingroup17formmonoatomicionswitha-1charge
Example:Cl-,F-,I-
Cations
Monatomiccationsareformedfrommetallicelements
Na+-sodiumion
Zn2+-zincion
Someelementscanformmorethanonecation
ThechargeontheionisindicatedbyaRomannumeralinparenthesesfollowedbythenameofthemetal
Fe2+-iron(II)ion
Fe3+-iron(II)ion
Transitionmetalsoftenformtwoormoredifferentmonoatomiccations
Anions
Monoatomicanionsaretypicallyformedfromnonmetals
Namedbydroppingtheelementnameendingandadding–ide
Cl--chlorideion
F--fluorideion
Commonpolyatomicanions
OH–hydroxideion
CN–cyanideion
Manypolyatomicanionscontainoxygen,theyarecalledoxyanions
Inelementsthatformtwodifferentoxyanions,thenameoftheonethatcontainsmoreoxygenendsin-ate,theonewithlessendsin-ite:
NO2--nitriteion
NO3--nitrateion
Somecompoundshavemultipleoxyanionforms
ClO--hypochloriteion,prefix“hypo”addedtotheoxyanionwiththeleastnumberofoxygen,suffix“-ite”
ClO2--chloriteion
ClO3--chlorateion
ClO4--perchlorateion,prefix“per”addedtothe
oxyanionwiththehighestnumberofoxygen,suffix“-ate”
Manypolyatomicanionswithhigh(negative)chargescan
addoneormorehydrogencations(H+)toformanionswithlowernegativecharge,theirnamingreflectswhethertheH+additioninvolvesoneormorehydrogenions
HSO4--hydrogensulfateion
H2PO4--dihydrogenphosphateion
Acids
AccordingtotheBronsted-Lowerydefinition,anacidisprotondonating(donatesH+).
Anionswithnamesendingin-idehaveassociatedacidsthathavethehydro-prefixandan-icsuffix:
Cl--chlorideion
HCl–hydrochloricacid
Acidsofoxyanions
Iftheoxyanionhasan-ateending,thecorrespondingacidisgivenan-icending
Iftheoxyanionhasan-iteending,thecorrespondingacidhasan-ousending
Prefixesusedinthenamingoftheanionarekeptinthenameoftheacid
ClO--hypochloriteion,HClO-hypochlorousacid
ClO2--chloriteion,HClO2-chlorousacid
ClO3--chlorateion,HClO3chloricacid
ClO4--perchlorateion,HClO4-perchloricacid
MolecularCompounds
Apairofelementscanformseveraldifferentmolecularcompounds
Prefixesareusedtoidentifytherelativenumberofatomsinthesecompounds
COcarbonmonoxide
CO2carbondioxide
Prefixes
Hydrates
Hydratesarecompoundsthatcontainswatermoleculeschemicallyboundtoanothercompoundorelement
Hydratesarefirstnamedfromtheanhydrous(dry)compound
Itisthenfollowedbytheword“hydrate”andaprefixtoindicatethenumberofwatermolecules
CuSO4•5H2O–copper(II)sulfatepentahydrate
MonoatomicCationsandAnions
PolyatomicIons:
MorePolyatomicIons
OxyanionsandtheirAcids
ChemicalEquations
Chemicalreactionsareexpressedthroughchemicalequations
Anarrow(“→”)inachemicalequationmeans“yields”
2H2(g)+O2(g)→2H2O(l)
Hydrogen+oxygenyieldswater
H2andO2arereactants
Substancesthatundergochangeduringareaction
H2Oistheproduct
Substancesformedfromchemicalreactions
Commonphasenotation
g=gas
l=liquid
s=solid
BalancingChemicalEquations
BalancedchemicalequationsadheretotheLawofConservationofMatter
Abalancedequationhastohaveequalnumbersofeachtypeofatomonbothsidesofthearrow
Balancingisdonebychangingthecoefficients
Thecoefficienttimesthesubscriptgivesthetotalnumberofatoms
Iftherearenocoefficientsinfront,coefficientisequaltoone
Ifanatomdoesn’thaveasubscript,subscriptisequaltoone
Subscriptsareneverchanged
CHAPTER3–STOICHIOMETRYOFFORMULASANDEQUATIONS
MassandMoles
Inthemetricsystem,thestandardunitofmassisthegram(orkilogram).
Allelementshaveauniquemass(atomicweight)
Expressedaseitheratomicmassunits(amu)orgrams
Sameweightoftwodifferentelementsrepresentsadifferentnumberofatoms
Considerthereaction:H2+F2→2HF
Doesnotmeanthat1gramofhydrogenwillreactwith1gramoffluorinetoform2gramsofhydrogenfluoride
Inreality2.016gofhydrogenwillreactwith38.000goffluorinetoform40.016ghydrogenfluoride
2.016gofhydrogencontainthesamenumberofH2moleculesas38.000goffluorine(F2)
40.016gramsofHFwillcontaintwiceasmanymolecules
Numberofmolecules,eveninlowmasses,areextremelylargenumbers
Soforconvenience,amountsinchemistryareexpressedinmoles
Mole-quantityofasubstancethatcontainsthesamenumberofatoms,moleculesorformulaunitsasexactly12gofcarbon-12
1mole(mol)=6.0221x1023
Atomicmass–massofonemolecule
Expressedinatomicmassunits(amu)
Molarmass–massofonemoleofentities(atoms,molecules,formulaunits)ofasubstance
Expresseding/mole
Molarmassandatomicmassarenumericallysimilar
Example:onemoleculeofcarbonhasanatomicmassof12.0107amuandamolarmassof12.0107g/mol
In12.0107gofcarbonthereare6.0221x1023molecules
MassPercentage(PercentComposition)
Masspercentageisawayofexpressingtheconcentrationofanelementinacompoundoracompoundofamixture.Stepsforsolvingpercentcomposition(akamasspercentage)questions:
ExampleQuestion:FindthemasspercentagesofC,O,andHinglucose(C6H12O6)
First,lookuptheatomicmassesoftheelementsthatareinthecompoundonaperiodictable
C–12.01g
H–1.01g
O–16.00g
Second,determinehowmanygramsofeachelementareinonemoleofglucose(orwhatevercompoundaquestionmaybeaskingyoufor)
C–(6molesofCx12.01g)=72.06g
H–(12molesofHx1.01g)=12.12g
O–(6molesofOx16.00g)=96.00g
Third,determinethetotalmassinonemoleofthecompoundbyaddingupthemassesoftheelementsfromstep2
Massofonemoleofglucose=180.18g(72.06g+12.12g+96.00g)
Finally,findthemasspercentagesoftheelementsbydividingtheweightofeachelementinonemoleofthecompoundbythemolarmassofthatcompound
C–(72.06g/180.18)x100%=39.99%
H–(12.12g/180.18)x100%=6.73%
O–(96.00g/180.18)x100%=53.28%
Tocheckyourworkyoucanaddupthepercentagestoseeiftheyaddupto100%
39.99%+6.73%+53.28%=100%
Formula
DeterminingEmpiricalFormula
Empiricalformulasarethesmallestwholenumberratioofnumbersoftheatomsinamolecule.Themolecularformulaofacompoundistheformulaofthecompoundasitexists,andmaybeamultipleoftheempiricalformula.
DeterminingEmpiricalFormulafromMasses
ExampleQuestion:Acompoundcontains36.42gofcarbon,6.12gofhydrogen,and47.89gofoxygen,whatisitsempiricalformula?
First,determinethemolesofeachelement
C–(36.42/12.01)=3.03
H–(6.12/1.01)=6.06
O–(47.89/16.00)=2.99
Second,determinethelowestwhole-numberratios;dividethemolesofeachelementbythelowestmoleamount
C–(3.03/2.99)=1.01→1
H–(6.06/2.99)=2.03→2
O–(2.99/2.99)=1.00→1
Thisstepusuallyresultsinratiosthatareveryclosetoawholenumber
However,insomequestionyoumaygetratiosof1.5,or2.5,or3.5,etc.inthiscaseyouwouldmultiplyalltheratiosby2togetwholenumberratios
Insomequestionyoumaygetratiosof1.33,or2.33,or3.33,etc.inthiscaseyouwouldmultiplyalltheratiosby3togetwholenumberratios
Ingeneralterms,iftheratiosarenotveryclosetoawholenumberyouhavetomultiplythembyanumberthatwouldresultinapproximatelywholenumbers
Writetheempiricalformulafromtheresults
CH2O
DeterminingEmpiricalFormulafromElementalAnalysis(%Composition)
ExampleQuestion:Acompoundisfoundtocontain56%carbon,7%hydrogen,and37%oxygen.Whatistheempiricalformulaforthiscompound?Themolecularweightforthiscompoundis86.14g/mol.Whatisthemolecularformula?
First,assumeexactly100gofthecompoundispresent
Thisallowsyoutoexchangepercentageswithgrams
C–56%→56g
H–7%→7g
O–37%→37g
Second,convertmassestomoles
C–(56/12.01)=4.66moles
H–(7/1.01)=6.93moles
O–(37/16.00)=2.31moles
Third,determinethelowestwhole-numberratios;dividethemolesofeachelementbythelowestmoleamount
C–(4.66/2.31)=2.02→2
H–(6.93/2.31)=3.00→3
O–(2.31/2.31)=1.00→1
Writetheempiricalformulafromtheresults
C2H3O
Todeterminethemolecularformulafromtheempiricalformulafollowthesesteps:
Calculatetheweightfromtheempiricalformula(multiplyatomsofeachelementwiththeelementsmolarmassandaddthemup)
2carbonatomsx12.01g=24.02g
3hydrogenatomsx1.01g=3.03g
1oxygenatomx16.00g=16.00g
Total:24.02g+3.03g+16.00g=43.05g
Dividethemolecularweightbytheweightdeterminedfromtheempiricalformulatofindthescalingfactor
86.14/43.05=2.00
Scalingfactoris2
Usingthescalingfactordeterminethemolecularformula
C4H6O2
StoichiometryStoichiometryinvolvesusingrelationshipsbetweenelements,compounds,chemicalformulas,andchemicalreactionstoacquirequantitativedata.Therearefourmajorcategoriesofstoichiometryproblemsthatyouarelikelytoencounter.Theyarelistedbelowwithstrategiesonhowtosolvethem.
ToconvertfromthemassofasubstancetomolesofthatsubstanceyoudividebythemolarmasToconvertfrommolesofasubstancetothemassofasubstanceyoumultiplybythemolarmass
Interconversion:
ThisinterconversionisveryimportantinchemicalcalculationsStoichiometricMole–MoleProblems
ExampleQuestion:HowmanymolesofHClareneededtoreactwith0.82molesofAl?
Writeoutachemicalequationfromtheinformationgiveninthequestion
Al+HCl→AlCl3+H2
Balancethechemicalequation
2Al+6HCl→2AlCl3+3H2
Calculatethemolesofthesubstanceyouaretoldtofindusingmoleratios
StoichiometricMass–MassProblems
ExampleQuestion:HowmanygramsofAlcanbecreatedfromdecomposing12.60gofAl2O3?
Writeoutachemicalequationfromtheinformationgiveninthequestion
Al2O3→Al+O2
Balancethechemicalequation
2Al2O3→4Al+3O2
Convertthemassofthegivensubstanceintomolesofthegiven(mol/g)
Calculatethemolesofthesubstanceyouaretryingtofindthemassforusingmoleratios
Calculatethemassofthesubstanceyouaretoldtofindusingthemolesofthesubstancecalculatedinthepreviousstep
StoichiometricMass-VolumeProblems
ExampleQuestion:HowmanylitersofH2arecreatedfromthereactionof40.00gofKinwater?
Important:1moleofanyidealgaswilloccupy22.41L
Writeoutachemicalequationfromtheinformationgiveninthequestion
K+H2O→KOH+H2
Balancethechemicalequation2K+2H2O→2KOH+H2
Convertthemassofthegivensubstanceintomolesofthegiven(mol/g)
Calculatethemolesofthesubstanceyouaretryingtofindthevolumeforusingmoleratios
Calculatethevolumeofthesubstanceyouaretoldtofindusingthemolesofthesubstancecalculatedinthepreviousstep
StoichiometricVolume-VolumeProblems
ExampleQuestion:HowmanylitersofSO2willbeproducedfrom28.3LO2?
Important:1moleofanyidealgaswilloccupy22.41L
Writeoutachemicalequationfromtheinformationgiveninthequestion
S2+O2→SO2
Balancethechemicalequation
S2+2O2→2SO2
Convertthevolumeofthegivensubstanceintomolesofthegiven(mol/g)
Calculatethemolesofthesubstanceyouaretryingtofindthevolumeforusingmoleratios
Calculatethevolumeofthesubstanceyouaretoldtofindusingthemolesofthesubstancecalculatedinthepreviousstep
LimitingReagent
Typicallyoneofthereactantsinachemicalreactionispresentinsmallerstoichiometricamountsthantheotherreactant(s)
Thislimitstheamountofproduct(s)thatcanform
Limitingreagentproblemsareeasytoidentify
Theproblemwillgivetheamountsofmorethanoneofthestartingmaterials
Youwillhavetodeterminethelimitingreagentfromcalculationsinordertosolvetheproblem
Therearetwotypicalmethodsofdeterminingthelimitingreagent
Needvs.HaveMethod
ProductMethod
Needvs.HaveMethod
Pickoneofthereactants(Reac1),calculatehowmuchoftheotherreactant(Reac2)youwillneedtocompletelyreactwithReac1
Utilizestoichiometricratios
Thisrequiresabalancedequation!
Makesuretheequationisbalancedbeforeyoubeginworkingontheproblem
ComparetheamountneededfortheReac2withtheactualamountlistedinthequestion
IftheamountyouneedisMOREthanwhatyouactuallyhaveavailableaccordingtotheproblemthenReac2isthelimitingreagent
IftheamountyouneedisLESSthanwhatyouactuallyhaveavailableaccordingtotheproblemthenReac1isthelimitingreagent
Youfinishtherestoftheproblembasedonthereactantyoufoundtobelimiting
“Product”Method
Pickoneoftheproductsofthereaction
Chooseoneofthereactants(Reac1)andcalculatehowmuchoftheproductyoucanmakeusingtheamountyouhaveavailableaccordingtothequestion
Makethesamecalculationusingtheotherreactant(Reac2)
Thereactantthatresultsinthesmallestamountofproductisthelimitingreagent
Theamountisalsothemaximumamountofproductthatcanbemade
Thisamountiscalledthe“theoreticalyield”
ReagentinExcess
Somequestionsmayaskyoutodeterminehowmuchoftheexcessreagentwillbeleftoveroncethereactionends
Tocalculatethisvalue
Calculatehowmuchoftheexcessreagentisneededtocompletelyreactwiththelimitingreagent
Takethedifference(subtract)offtheamountofexcessreagentyouhadatthebeginningandtheamountneededtocompletelyreactwiththelimitingreagent
PercentYield
Itisverycommonthattheamountofproductmadeexperimentallyislowerthantheamountexpectedbythetheoreticalyield
Thisoccursbecauseofmechanicalerrors,incompletereactions,“side”reactions,etc.
Todeterminethepercentyield(sometimesalsocalledtheefficiencyofareaction)usethefollowingformula:
CHAPTER4–CHEMICALREACTIONS
WaterasaSolvent
Mostreactionsthatoccurinorganismsandtheenvironmenttakeplaceinwater
Waterhas2hydrogenatomscovalentlybondedto1oxygenatom
Theelectronicstructureofwateristetrahedral
2covalentbondswithHatomsand2setsofunpairedelectrons
104.5˚bondangle–becausethetwolonepairstrytoseparateasfaraspossible
Waterisapolarmolecule
Polaratomshavedipolesbecauseofunequalsharingofelectrons
Thesharedpairofelectronsareattractedmorestronglytotheoxygenformingapartiallynegativecharged“pole”neartheoxygenandpartiallypositivelychargedpolesneartheHydrogens
StructureofWaterwithDipoles:
Solubility
Solublesubstances(solutes)inwater
Interactionbetweenanionandwaterisstrong
Polarcompoundsarewatersoluble
Polarwatermoleculeshaveanaffinityforoppositelychargedregionsofotherpolarmolecules
Insolublesubstances(solutes)inwater
Non-polarcompoundsarenotwater-soluble
Iftheinteractionbetweenionandwaterisweak
Insolublesubstanceshaveaforceofattractionsostrongintheirsolidsubstanceform,thatitcannotbeovercomebytheinteractionoftheionswiththepolarizedwatermolecules
IonsinAqueousSolution
Inionicsolids,cations&anionsareheldtogetherbyelectrostaticattraction
Theelectrostaticattractionisreplacedbywatermoleculesinanaqueoussolution
Manyioniccompoundsdissociateintoindependentionswhendissolvedinwater
Compoundsthatfreelydissociateintoindependentionsinaqueoussolutionarecalledelectrolytes
Solutionswithelectrolytesaregoodconductorsofelectricity
Notallelectrolytesareioniccompounds
Somemolecularcompoundsdissolvebutdonotdissociateintoions
Containpolarbondswhichinteractwiththepolarbondsinwater
Donotconductanelectriccurrent
Produceanonconductingsolution
Referredtoasnonelectrolytes
StrongandWeakElectrolytes
Strongelectrolyte-anelectrolytethatcompletelydisassociatesinsolution
Existinsolutionalmostentirelyasions
Weakelectrolyte-anelectrolytethatdoesnotcompletelydisassociateinsolution
Existsinsolutionasbothionsandmoleculesoftheelectrolyte
MolecularandIonicEquations
Molecularequationexpressreactantsandproductsasiftheyweremolecules,despiteactuallyexistinginsolutionasions
Exampleofamolecularequation
CaCl2(aq)+2AgNO3(aq)⇌ Ca(NO3)2(aq)+2AgCl(s)
(aq)isusedtoindicatethatthesubstanceisactuallydisassociatedinsolution
(s)isusedtoindicatethatthesubstanceisaprecipitate
Ionicequationexpressstrongelectrolytesasseparateindependentions
Exampleofanionicequation
Ca2+(aq)+2Cl-(aq)+2Ag+(aq)+2NO3-(aq)⇌ Ca2+
(aq)+2(NO3)-(aq)+2AgCl(s)
Notethatthesolidiswritteninitsfullformula
Netionicequationareequationswithoutanyspectatorions
Spectatorion-anioninanionicequationthatdoesnottakepartinthereaction
Easywayofidentifyingspectatorionsisbywritingtheionicequationandthencrossingoffanyionsthatappearonbothsidesoftheequation(thosearethespectatorions)
Example:
Ca2+(aq)+2Cl-(aq)+2Ag+(aq)+2NO3-(aq)⇌
Ca2+(aq)+2(NO3)-(aq)+2AgCl(s)
Resultingnetequation:2Cl-(aq)+2Ag+(aq)⇌ 2AgCl(s)
ThreeMajorClassesofChemicalReactions
Thethreemajorclassesofchemicalreactionsare:precipitationreactions,acid-basereactions,andoxidation-reductionreactions.
PrecipitationReactions
Precipitationreactionoccursinaqueoussolutionbecauseoneoftheproductinaprecipitationreactionisinsoluble
Precipitate-aninsolublesolidcompoundformedduringachemicalreactioninsolution
Therearegeneralizedsolubilityrulesthatareusedtopredictwhetheraprecipitatewillform
Soluble-allcompoundscontainingtheammoniumion(NH4
+)oralkalimetal(GroupIAontheperiodictable)cations
Soluble-allnitratesandacetates(ethanoates)
Soluble-allchlorides,bromidesandiodides
ExceptthosewithAg,Pb,Hg
Soluble-allsulfates
ExceptthosewithAg,Pb,Hg(I),Ba,Sr,Ca
Insoluble-allcarbonates,sulfites,andphosphates
Exceptthosewithammonium(NH4+),andalkali
metal(GroupIA)cations
Insoluble-allHydroxides
ExceptthosewithNH4+,alkalimetal(GroupIA)
cations
Insoluble-allsulfides
ExceptthosewithNH4+,alkalimetal(GroupIa)
cations,andalkaliearthmetal(GroupII)cations
Insoluble-alloxides
ExceptthosewithCalcium,Barium,andalkalimetal(groupIA)cations
SolubilityRulesTables:
Precipitationreactionstaketheformofan“exchangereaction”
Exchangereactionsarereactionbetweencompoundsthatappeartoinvolveanexchangeofcationsandanions
Acid-BaseReactions
TheArrheniusdefinitionofacidsandbases
Acidsproducehydrogenions(H+)whendissolvedinwater
Basesproducehydroxideions(OH-)whendissolvedinwater
Bronsted-Lowerydefinitionofacidsandbases
Acidsareprotondonating
Basesareprotonaccepting
Strongacid–anacidthationizescompletelyinwater
StrongacidsareHI,HBr,HClO4,HCl,HClO3,H2SO4,andHNO3
Weakacid–anacidthatonlypartiallyionizesinwater
Strongbase–abasethatispresentalmostentirelyasions(oneoftheionsisOH-)
StrongbasesareNaOH,KOH,LiOH,RbOH,CsOH,Ca(OH)2,Ba(OH)2,andSr(OH)2
Weakbase–abasethatonlypartiallyionizesinwater
Strongacidsandbasesarerepresentedasseparateionsinanionicequation
Weakacidsandbasesarerepresentedasundissociated“molecules”inionicequations
ExampleofAceticAcid(aweakacid)
MolecularEquation:CH3COOH(aq)+NaOH(aq)→
CH3COONa(aq)+H2O(l)
Ionic:CH3COOH(aq)+Na+(aq)+OH-(aq)→CH3COO-(aq)+
Na+(aq)+H2O(l)
Net:CH3COOH(aq)+OH-(aq)→CH3COO-(aq)+H2O(l)
Neutralization(Acid-Base)Reactions
Acidsandbasesneutralizeoneanother
Neutralizationreaction-reactionbetweenanacidandabasethatresultsinanioniccompoundandwater
Salt-ioniccompoundthatistheproductofaneutralizationreaction
Netionicequationforeachneutralizationreactioninvolvesatransferofaproton
ConsidertheexampleofHCl(astrongacid)reactingwithLiOH(astrongbase)
Netequationforthereactionis:H+(aq)+OH-(aq)→
H2O(l)
ConsidertheexampleofHCN(aweakacid)reactingwithKOH(aweakbase)
HCN(aq)+OH-(aq)→CN-(aq)+H2O(l)
TheprotonistransferredfromHCNtoOH-
Acid-BaseReactionswithGasFormation(akaDisplacementReactions)
Acid-basereactionswithgasformationsometimesinvolveunstablechemicalspecies(e.g.,H2CO3andH2SO3
Unstablespeciesareenclosedinparentheses
Example:[H2CO3(aq)]→H2O(l)+CO2(g)
Oxidation-ReductionReactions(akaRedoxReactions)
Oxidation-reductionreactions(akaredoxreactions)–reactionsthatinvolveapartialorcompletetransferofelectronsfromonereactanttoanother
Oxidation=lossofelectrons
Reduction=gainofelectrons
Trickforrememberingwhichiswhich-OILRIG
OIL-OxidationIsLosingelectrons
RIG-ReductionIsGainingelectrons
Oxidationandreductionalwaysoccursimultaneously
Oxidationnumber(akaoxidationstate)–actualchargeanatominamoleculewouldhaveifalltheelectronsitwassharingweretransferredcompletely,notshared
Oxidizingagent–speciesthatoxidizesanotherspecies
Itisitselfreduced
Reducingagent–speciesthatreducesanotherspecies
Itisitselfoxidized
ReducingandOxidizingAgents:
OxidationNumberRules
CommonRedoxReactions
Combination-reactioninwhichtwosubstancecombinetoformathirdsubstance
Decomposition–reactioninwhichasinglecompoundproducestwoormoresubstances
Displacement(akasingle-replacementreaction)–reactioninwhichanelementreactswithacompoundanddisplacesanelementfromit
Combustion–reactioninwhichoneofthereactantsisoxygen
Usuallyresultsintherapidreleaseofheat
Redoxreactionscanbewrittenintermsoftwohalf-reactions
Oneinvolvesthelossofelectrons(oxidation)
Theotherinvolvesthegainofelectrons(reduction)
Example:Fe2++Ce4+→Fe3++Ce3+
Abalancedredoxequationhastohavechargebalance
Numberofelectronslostintheoxidationhalf-reactionmustbeequaltothenumberofelectronsgainedinthereductionhalf-reaction
CHAPTER5–QUANTUMTHEORYANDATOMICSTRUCTURE
EmissionSpectrum
Whenelementsareburnedinaflameandtheiremissionsarepassedthroughaprismonlyafewcolorlinesareseen
Theselinesareadistinctcharacteristicofeachelement
Atomsemitlightofacharacteristicwavelengthswhentheyreturnfromanexcitedstatetotheirgroundstate
EmissionSpectrumofHydrogen:
LightLightisaformofelectromagneticenergythatbehavesasbothawaveandaparticle.
LightasaWave
ElectromagneticenergytravelsinrhythmicwaveswhicharedisturbancesofelectricandmagneticfieldsWavelength(λ)-distancebetweenconsecutivecrestsofelectromagneticwaves
Wave:
Frequency(f)–numberofcrestsofawavethatmovepastagivenpointinagivenunitoftime
f=λ/vv=speed
Speedoflightinavacuum=2.998x108m/secTheelectromagneticspectrumencompassesaverywiderangeofwavelengthsfromassmallasananometertothosethataremorethanakilometer
LightasaParticle
LightalsobehavesasifitconsistsofdiscreteparticlesorquantacalledphotonsEachphotonhasafixedquantityofenergy
E=hc/λhisthePlanck’sconstant=6.626X10-34joules•seccisthespeedoflightinavacuum=2.998X108m/sec
Shorterλ=higherenergy
Wave-ParticleDualityAllmatterandenergyexhibitbothwaveandparticle-likepropertiesThisdualityisseenin:
MacroscopicobjectsMicroscopicobjects(e.g.atomsandmolecules)Quantumobjects(e.g.,protons,neutrons,quarks,mesons)
ToexplainWave-ParticlesDuality,physicistsfocusedon3phenomena
BlackBodyRadiationPhotoelectricEffectAtomicLineSpectra
BlackBodyRadiation
Asthetemperatureofanobjectchanges,itstemperatureisdirectlyrelatedtothewavelengthsoflightthatitemits.Thisisacharacteristicoftheidealized“blackbody.”
MaxPlanckdevelopedamathematicalmodeltoreproducethespectrumoflightemittedbyglowingobjects
Themodelwasdevelopedundertheassumptionthatavibrating(oscillating)atomcanonlyemitorabsorbcertainquantitiesofenergy
Planck’sModel
E=nhv
E-energyofradiation
v–frequency
n–quantumnumber(1,2,3…)
h–Planck’sConstant=6.626x10-34J•s
Quanta–packetsofenergythatcanbeemittedorabsorbed
Atomschangeenergystateswhentheyemitorabsorboneormorequanta
Themodelviewsemittedenergyaswaves
PhotoelectricEffect
Thephotoelectriceffectistheobservationthatmanymetalsemitelectronswhenlightshinesuponthem.Electronsemittedinthismannerarecalledphotoelectrons.
Electronsareejectedfromthesurfaceofthemetalonlywhenthefrequencyexceedsacertainthreshold
Thethresholdisdependentonthecharacteristicofthemetal
Einsteinreasonedthatatomschangeenergystateswhentheyemitorabsorbaquantumoflightenergy,whichhecalledaphoton
Hedefinedaphotonasaparticleofelectromagneticenergy
Accordingtothephotoelectriceffect
Electronsexistindifferentenergystates
Aphotonwhosefrequencyisgreaterthanorequaltotheenergystateoftheelectronwillbeabsorbed
Ifthefrequencyislessthantheelectronenergylevel,thephotonisnotabsorbed
Theelectronmovestoahigherenergystateandisejectedfromthesurfaceofthemetalwhenitabsorbsaphoton
Electronsareattractedtothepositiveanodeofabatterywhichcausesaflowofcurrent
AtomicLineSpectra
Whenlightfroman“excited”atompassesthroughaprism,itdoesnotformacontinuousspectrum
Instead,itproducesaseriesofcoloredlinescalled“linespectra”thatareseparatedbyblackspaces
Wavelengthsofthelinesareacharacteristicoftheelementsproducingthem
Differentelementshavedifferentlinespectra
ExampleofHydrogen
ThespectralinesofHydrogenoccurinseveralseries
Eachseriesisrepresentedbyapositiveinteger,n
LineSpectraofHydrogen:
Ultravioletseries,n=1
Visibleseries,n=2
Infraredseries,n=3
ThevisiblespectrumofHydrogencanbereproducedbyaRydbergEquation
R–RydbergConstant=1.096776x107
m-1
Λ–wavelengthofthespectraline
n1andn2arepositiveintegerswheren2>n1
BohrTheory
Bohr’stheoryofanatomwasanearlymodelofatomicstructureinwhichelectronstravelaroundthenucleusinanumberofdiscretestableorbitsdeterminedbyquantumconditions.
Bohrcameupwith2postulatestoaccountforhowelectronsloseenergyyetremaininorbit
Aelectronhasspecificenergylevelsinanatom
Aelectroninanatomchangesenergylevelsbyundergoingatransitionfromoneenergyleveltoanother
Bohrcameupwithaformulafortheenergylevelsoftheelectroninthehydrogenatom
E=-2.18x10-18J
n–principalquantumnumbers=1,2,3…
Z–nuclearcharge
Z=1forHydrogen
Whenanelectronundergoesatransitionfromahigherenergylevel(ni)toalowerone(nf)theenergyisemittedasaphoton
E=hv=Ef–Ei=∆E
E–energyofemittedphoton
Ei=
Ef=
∆E=hv=-2.18x10-18J
QuantumMechanics
Quantummechanicsisthebranchofphysicsthatattemptstomathematicallydescribethewavepropertiesofsubmicroscopicparticles.
deBroglierelation
λ=h/mv
Matterhaswave-likepropertiesbutthesepropertiesarenotcommonlyobserved
deBroglierelationshowsthatthewavelengthofobjectsissoincrediblysmallthatthesewavescannotbedetected
Heisenberg’sUncertaintyPrinciple
Statesthatyoucanneverknowtheexactpositionandtheexactspeedofanobjectwithhighprecision
Essentially,thereisanuncertainty
Theprincipleisalsoarelationshipthatstatesthattheproductoftheuncertaintyinposition(∆x)andtheuncertaintyinmomentum(m∆vx)ofaparticlecanbenosmallerthanwhatispredictedbytheequation:
(∆x)(m∆vx)>
=5.28x10-35J•s
Whenmislarge(representsalargeobject)theuncertaintyisverysmallbutforsubatomicparticleslikeelectronthereisahighlevelofuncertainty
Thisuncertaintyiswhywecan’tdefinetheexactorbitofanelectron
Schrodingerdevelopedaquantummechanicalmodelofthehydrogenatom.Accordingtothemodel:
Anatomhasspecificallowedquantitiesofenergy
Anelectron’sbehavioriswave-like
However,itsexactlocationisimpossibletoknow
Theelectron’sMatter-Waveoccupiesa3-Dspacenearthenucleus
TheMatter-Waveexperiencescontinuousandvaryinginfluencefromthenuclearcharge
SchrodingerEquation
H(op)Ψ=EΨ
E–energyoftheatom
Ψ–wavefunction
H(op)–HamiltonianOperator
QuantumNumbersandAtomicOrbitals
Quantummechanicsdescribeseachelectronby4quantumnumbers
PrincipalQuantumNumber(n)
AngularMomentumQuantumNumber(l)
MagneticQuantumNumber(m l )
SpinQuantumNumber(ms)
n, l ,m l definethewavefunctionoftheelectron’s
atomicorbital
msreferstothespinorientationofthe2electronsthatoccupyanatomicorbital
PrincipalQuantumNumber(n)representsthe“shellnumber”inwhichanelectronislocated
Representstherelativesizeoftheorbital
Definestheprincipalenergyoftheelectron
Smaller“n”representsasmallerorbitalandalowerenergyoftheelectron
ncantakeanypositivevalue
AngularMomentumQuantumNumber( l )representsthe“subshells”withinagivenshell
Eachmain“shell”isdesignatedbyaquantumnumber“n”
Itisfurthersubdividedinto:l =n-1“subshells”
“ l ”canhaveanyintegervaluefrom0ton-1
“ l ”valuescorrespondtothes,p,d,fdesignationsusedintheelectronicconfigurationoftheelements
shasan l valueof0
phasan l valueof1
dhasan l valueof2
fhasan l valueof3
MagneticQuantumNumber(m l )definesatomicorbitalswithinagivensub-shell
Eachvalueoftheangularmomentumnumber( l )determinesthenumberofatomicorbitals
Foranygivenvalueof“ l ,”mlcantakeanyintegervaluefrom- l to+ l
m l =- l to+ l
Eachorbitalhasadifferentshapeandorientation(x,y,z)inspace
Eachorbitalwithinagivenangularmomentumnumbersubshell( l )hasthesameenergy
SpinQuantumNumber(ms)representsthetwopossiblespinorientationsofanelectronresidingwithinagivenatomicorbital
Eachatomicorbitalholdsonlytwoelectrons
Eachelectronhasa“spin”orientationvalue
Thesevaluesmustbeoppositeofoneanother
Possiblevaluesofmsare:+½and-½
SummaryofQuantumNumbers
Shapesoforbitals
s(n=1)subshellorbital
Onlyoneorbital,holds2electrons,sphericalshape
p(n=2)subshellorbitals
Threeorbitals,holds6electrons,dumbbellshape
d(n=3)subshellorbital
Fiveorbitals,holds10electrons,pear-shapedlobesanddumbbellshapes
f(n=4)subshellorbitals
Sevenorbitals,holds14electrons
CHAPTER6–ELECTRONCONFIGURATION
ANDPERIODICPROPERTIES
BriefReviewtoUnderstandElectronConfiguration
Thequantumnumbersn, l ,m l defineanorbital
Aorbitalcontainsamaximumof2electrons
Eachelectronhasadifferentspin(+½or-½)
Orbitaldiagramsarenotationsusedtoshowhowtheorbitalsofasubshellareoccupiedbyelectrons
Eachgroupoforbitalsislabeledbyitssubshellnotation(s,p,d,f)
Electronsarerepresentedbyarrows
Up↑forms=+½
Down↓forms=-1/2
ExampleofanOrbitalDiagram:
PauliExclusionPrinciple
Notwoelectronsinanatomcanhavethesamefourquantumnumbers
Summarytableforthemaximumnumberofelectronsineachsubshell:
ElectronConfigurationTheelectronconfigurationofanatomreferstotheparticulardistributionofelectronsamongtheavailablesubshellinthatatom.
Electronicconfigurationnotationlistssubshellsymbols(s,p,d,f)sequentiallywithasuperscripttoindicatethenumberofelectronsinthatsubshell
Ex.Fluorine
AtomicNumber:9
NumberofelectronsinaneutralFluorineatom:9
Numberofelectronsforaneutralatomisthesameastheatomicnumber
2electronsinthe“1s”subshell
2electronsinthe“2s”subshell
5electronsinthe“2p”subshell
ElectronConfiguration:1s22s22p5
Configurationscanbecomequitecomplexasatomicnumberincreases
Toremedythis,acondensedformoftheconfigurationisoftenusedwhichutilizeselectronconfigurationsofnoblegases
Noblegaseshavethemaximumnumberofelectronspossibleintheiroutershell
Makesthemveryunreactive
Thenoblegasesare:helium,neon,argon,krypton,xenon,andradon
TableofCondensedElectronicConfigurationExamples:
[X]representstheelectronconfigurationofthenearestnoblegasthatappearsbeforetheelementofinterestontheperiodictable
Keepinmindthatyouhavetoadjustthenumberofelectronsandthustheelectronconfigurationforcationsandanionsofanelement
NuclearCharge,ShieldingEffect,andOrbitalShapeNuclearCharge
Inanatomthereare2counteractingforces:
Inthenucleus
Positiveprotonspull(attract)thenegativelychargedelectrons
Outsidethenucleus
Negativelychargedelectronsarerepellingeachother
Highernuclearcharge(Z)lowersorbitalenergybyincreasingtheamountofproton-electronattractions
Loweringorbitalenergymakesitmoredifficulttoremovetheelectronfromorbit
ShieldingEffect
Therepulsionelectronsexperiencefromotherelectronsshields(counteracts)theattractiveforceoftheprotonsinthenucleus
Shieldinglowersthefullnuclearchargetoan“effectivenuclearcharge”(Zeff)
Loweringtheeffectivenuclearchargemakesiteasiertoremoveanelectron
IttakeslessenergytoremoveanelectronfromHelium(He)thanfromHe+
SincethesecondelectroninHerepelsthefirstelectronandeffectivelyshieldsthefirstelectronfromthefullnuclearcharge
EffectsofOrbitalShape
Shapeofanatomicorbitalaffectshowcloseanelectroncomestothenucleus(i.e.thelevelofpenetration)
Penetrationandshieldingcausetheenergylevel(n)tobesplitintosublevelsofdifferingenergy
Thisisrepresentedbythevariousvaluesofthemagneticquantumnumber( l )
Thelowerthevalueofthemagneticquantumnumber,thegreatertheelectronpenetration
OrderofSublevelEnergies
s( l=0)<p( l=1)<d( l=2)<f( l=3)
AufbauPrinciple
TheAufbauprinciplestatesthatelectronsorbitingoneormoreatomsfillthelowestavailableenergylevelsbeforefillinghigherlevels.Forexample,anelectronhastofillthe“1s”before“2s.”
Fillingorbitalsofthelowestenergyfirstgivesthelowesttotalenergyoftheatom
Thegroundstateoftheatom
Orderinwhichthepossiblesubshellsfill
1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f
OrderofFillingSubshells:
Orderinwhichsubshellsarefilledisintheorderinwhichthediagonallinesgothroughthesubshells
Note:4ssubshellisfilledbeforethe3dsubshellbecause4selectronsareatalowerenergylevelthanthe3delectrons
Lowerenergylevelsarealwaysfilledfirst
Configurationassociatedwiththelowestenergylevelofanatomisthegroundstate
Anyotherconfigurationscorrespondtotheexcitedstates
Hund’sRuleHund’srulestatesthatthe“groundstate”(i.e.thelowestenergyconfiguration)ofelectronsinasub-shellisattainedfromputtingelectronsintoseparateorbitalsofasubshellbeforepairingtheelectrons.
Example:OxygenOxygenOrbitals:
Note:Twooftheelectronsinthe2porbitalsappearsinglyinsteadofbeingpairedtogether
AccordingtoHund’sRule,electronsoccupyseparateorbitalsratherthanpairingwhenpossible
ConfigurationsandthePeriodicTable
Electronsinanatom’soutermostshellarecalledvalenceelectrons
Valenceelectronsaretheelectronsprimarilyinvolvedinchemicalreactions
Elementswithinagrouphavethesamevalenceshellconfiguration
Thisiswhygroupsofelementssharechemicalproperties
Noblegaseshavefilledoutershells
Veryhighionizationenergies
Positive(endothermic)electronaffinities
Donotreadilyformionsorreact
Inertforthemostpart
Verystable
Otherelementstrytoattainnoblegasconfiguration(filledoutershells)forstability
ElementsinGroups1Aand2Areadilyformcationsbylosingelectrons
Theyonlyhave1or2electronsintheiroutershellsrespectively,losingtheirvalenceelectronsallowstheseelementstoconformtonoblegasconfiguration
ElementsinGroups6Aand7Areadilyformanionsbygainingelectrons
Theyfilltheiroutershellsandconformtoanoblegas
configuration
Theyareisoelectronicwiththenearestnoblegasconfiguration
Isoelectronic–havethesamenumberofelectronsorthesameelectronicstructure
LargemetalsfromGroups3A,4A,and5Aformcationsthroughadifferentprocessthanthesmaller1Aand2Aelements
Theyhavetoloselargeamountsofelectronsinordertoattainnoblegasconfiguration
Example:Tin(Sn),wouldhavetolosetwoelectronsfrom5p,tenfrom4d,twofrom5sinordertobeisoelectronicwithKrypton
ForTinitiseasiertogainstabilitybyreachinganoblegas-likeconfigurationbyhavingempty5s&5psublevelsandafilledinner4dsubshellconfiguration
Manytimesitisonlyimportanttoknowthevalenceelectronnumberforanatom
Ontheperiodictableitiseasytodeterminethis:thenumberofvalenceelectronsforanatommatchesitsgroupnumber
Example:Group7Aelementshave7valenceelectrons
PeriodicProperties
PeriodicLawstatesthatwhenelementsarearrangedbyatomicnumber,theirphysicalandchemicalpropertiesvaryacrosstheperiodictablerow.
AtomicSize
Twofactorsthataffectsizeofanatom
Largertheprincipalquantumnumber(n),thelargerthesizeoftheorbit
Effectivenuclearcharge
Positivechargeanelectronexperiencesfromthenucleusminusanyshieldingeffects
Atomicradiustendstodecreasewithincreasingatomicnumberacrossaperiod
Thereisahighereffectivenuclearcharge
Greaterattractiveforceinthenucleusfromthehighernumberofprotons
Atomicradiustendstoincreasewithincreasingatomicnumberwithinagroup
Moreenergylevels
Eachsubsequentenergylevelisfurtherfromthenucleusthanthelast
IonicSize
Cationsaresmallerthantheirneutralatomcounterparts
Electronsareremoved
Resultsinadecreaseinelectronrepulsion
Allowsnuclearchargetopullelectronscloser
Anionsarebiggerthantheirneutralatomcounterparts
Electronsareadded
Resultsinanincreaseinelectronrepulsion
Occupymorespace
Ionicsizeincreasesdownagroup
Moreenergylevels
Ionicsizeisslightlycomplicatedacrossaperiod
Decreasesamongcations
Increasesdramaticallywiththefirstanion
Decreaseswithinanions
IonizationEnergy(IE)
Firstionizationenergy-theminimalenergyneededtoremoveoneoftheoutermostelectronsfromaneutralatom
Successiveelectronremovaliscalledsecondionizationenergy,thirdionizationenergy,etc.
Successiveionizationenergiesincreasebecauseeachelectronthatispulledawaycreatesalargerpositivecharge(i.e.ahighereffectivenuclearcharge)
Ionizationenergiestendincreasewithatomicnumberwithinaperiod
Moredifficulttoremoveanelectronthatisclosertothenucleus
Remember:Thereisahighereffectivenuclearchargeacrossaperiod
Ionizationenergiestendtodecreasedownagroup
ElectronAffinity
Thisisnotthesameaselectronegativity!
Morenegativeelectronaffinityvalueexpressthatamorestablenegativeionisformed
Negativevaluesindicatethatenergyisreleasedwhentheanionforthatelementforms
Generaltrendisthatvaluesbecomemorenegativefromlowerlefttoupperright
HighestelectronaffinitiesoccurforFandCl
Electronegativity
Electronegativityisthemeasureofanatom’sabilityoftodrawbondingelectronstoitselfinamolecule
Electronegativitytendstoincreasefromthelower-leftcornertothe
upper-rightcorneroftheperiodictable
Metals,NonMetals,andMetalloidsMetals
TypicalProperties
Shinysolids
Highmeltingpoints
Goodthermal&electricalconductors
Malleable
Losetheirelectronstononmetals
NonMetals
TypicalProperties
Notshiny
Lowmeltingpoints
Poorthermal&electricalconductors
Crumblysolidsorgases
Gainelectronsfrommetals
Metalloids(Semi-metals)
Elementsthatexhibitsexternalcharacteristicsofametal,butbehaveschemicallyasanonmetal
TypicalProperties
Makegoodsemiconductors
Haveintermediateconductivity
Intermediateelectronegativityvaluesandionizationenergies
Reactivitydependsontheelementwithwhichtheyarereacting
Donotformmultiplebonds
Compoundswithmetalloidsoftenhaveincompleteoctetaroundthecentralatom
Boilingpoints,meltingpoints,anddensitiesvarywidely
MetallicBehaviorTrends
Metallicbehaviordecreasesacross(lefttoright)aperiodandincreasesdownagroup
CHAPTER7–CHEMICALBONDING
IonicBonds
Ionicbondsarechemicalbondsformedbytheelectrostaticattractionbetweenpositiveandnegativeions.
Ionicbondsinvolvethetransferofelectronsfromoneatomtoanother
UsuallythetransferisfromametalfromGroupIAorIIAtoanonmetalfromGroup7AorthetopofGroup6A
Numberofelectronslostorgainedbyanatomisdeterminedbyitsneedtobeisoelectronicwithitsnearestnoblegas
Noblegasconfigurationsareextremelystable
Ionicbondsresultintheformationofionsthatareelectrostaticallyattractedtooneanother
Anion–negativelychargedion
Sizeofananionislargerthantheoriginalsizeoftheneutralatom
Cation–positivelychargedion
Sizeofacationissmallerthantheoriginalsizeoftheneutralatom
PropertiesofIonicCompounds
Hard:don’tdent
Rigid:don’tbend
Brittle:crackbutdon’tdeform
Theabovepropertiesarearesultofthepowerfulattractiveforcesholdingionstogether
Movingionsoutofpositionrequireslargeamountsofenergytoovercometheattractiveforces
CovalentBonds
Twononmetalsoftenformcovalentbonds
Shareelectronssincetheyhavesimilarattractionsforthem
Eachnonmetalholdstightlytoitsownelectrons
Sharedelectronpairspendmostoftheirtimebetweenthetwoatoms
Electronpairsbeingsharedaresaidtobelocalized
Howcovalentbondsform
Distancebetweentwonucleidecreases
Eachstartstoattracttheother’selectron(s)
Causesadecreaseinpotentialenergy
Atomsdrawcloserandclosertogether
Energybecomesprogressivelylower
Attractionsincreasebutsodoesrepulsionsbetweenelectrons
Ataparticularinternucleardistance,maximumattractionisachieved
Balancebetweennucleus-electronattractions
Balancebetweenelectron-electronandnucleus-nucleusrepulsions
Twosetsofforcesareinvolvedwithincovalentcompounds
Strongcovalentbondingforcesholdatomstogetherwithinthemolecule
Weakintermolecularforcesholdseparatemoleculesneareachother
Weakintermolecularforcesbetweenmoleculesareresponsiblefortheobservedphysicalpropertiesofthesemolecules
TypesofCovalentBonds
Coordinatecovalentbond–covalentbondinwhichbothofthesharedelectronsaredonatedbyasingleatom
Doublebond–sharingoftwopairsofelectronsbetweenatoms
Triplebonds–sharingofthreepairsofelectronsbetweenatoms
Polarcovalentbond–covalentbondwherethebondingelectronspendmoretimeclosertooneoftheatomsinvolvedinthebonding
Nonpolarcovalentbond–covalentbondwherethebondingelectronsaresharedequally
BondingPairsandLonePairs
Sharedelectronsareconsideredasbelongingentirelytoeachatominacovalentbond
Sharedelectronpairsimultaneouslyfillstheouterlevelofbothatoms
Anouter-levelelectronpairthatisnotinvolvedinbondingisa“lonepair”
Metal-MetalBondingMetalshavelowionizationenergies
LoseelectronseasilyDonotgainthemreadily
Valenceelectronsareevenlydistributedaroundmetal-ioncoresMetal-ioncoresconsistofthenucleusplustheinnerelectrons
ValenceelectronsaredelocalizedMovefreelythroughoutthemetal
PredictingIonicandCovalentBonding
Non-polarcovalentbond
Typicallyelectronegativitydifferencebetweenthetwoatomshastobelessthan0.5fornon-polarbonds
Polarcovalentbonds
Electronegativitybetweenthetwoatomsisdifferentbyagreaterdegreethan0.5butlessthan2.0
Ionicbonds
Typically,differenceinelectronegativityismorethan2.0
BondLength,BondOrder,andBondEnergy
Bondorder-measureofthenumberofbondingelectronpairsbetweenatoms
Singlebondshaveabondorderof1
Doublebondshaveabondorderof2
Triplebondshaveabondorderof3
Fractionalbondordersarepossibleinmoleculesandionsthathaveresonancestructures
Bondlength(akabonddistance)–distancebetweenthenucleiinabond
Bondlengthdependsonbondsorder
Increaseinbondordermeansashorterandstrongerbond
BondEnergy(BE)–measureoftheamountofenergyrequiredtobreakapartonemoleofcovalentlybondedgases
Quantityofheatabsorbedtobreakreactantbondsisdenoted∆H˚reactants
Quantityofheatreleasedtoformproductbondsisdenoted∆H˚products
Exothermicreactions
∆H˚rxnisnegative
Endothermicreactions
∆H˚rxnispositive
CHAPTER8–GEOMETRYOFMOLECULES
LewisDotStructures
LewisStructureofCarbon:
Lewisdotstructuresrepresentelectronsinthevalenceshellofanatomorionasdotsplacedaroundthelettersymboloftheelement
Bondingelectronpairsarerepresentedbyeithertwodotsoradash
LewisElectron-dotFormulaExample:
RulesforFormingLewisStructures
Calculatethenumberofvalenceelectronsforthemolecule
Group#foreachatom(1-8)
Givesvalenceelectronnumberforeachatom
Addallnumbersup
Addthechargeofanyanions
Example:ananionwitha-2chargehas2extraelectrons,youwouldadd2tothetotalcount
Subtractthechargeofanycations
Example:acationwitha+3chargelacks3electrons,youwouldsubtract3fromthetotalcount
Placetheatomwiththelowestgroupnumberandlowestelectronegativityasthecentralatom
Arrangetheotherelementsaroundthecentralatom
Distributeelectronstoatomssurroundingthecentralatomtosatisfytheoctetruleforeachatom
Distributetheremainingelectronsaspairstothecentralatom
Ifthecentralatomisdeficientinelectrons,completetheoctetforitbyformingdoublebondsorpossiblyatriplebond
OctetRule
Theoctetrulestatesthatthetendencyofatomsinamoleculeistohaveeightelectronsintheiroutershell.
Thereareexceptionstothisrulewherethecentralatommayhavemorethaneightelectrons
Generally,anonmetalinthethirdperiodorhighercanaccommodateasmanyastwelveelectrons,ifitisthecentralatom
Theseelementshaveunfilled“d”subshellsthatcanbeusedforbonding
Resonance(DelocalizedBonding)
StructuresofsomemoleculescanberepresentedbymorethanoneLewisdotformula
IndividualLewisstructuresarecalledcontributingstructures
Individualcontributingstructuresareconnectedbydouble-headedarrows(akaresonancearrows)
Moleculeorionisahybridofthecontributingstructuresanddisplaysdelocalizedbonding
Delocalizedbondingiswhereabondingpairofelectronsisspreadoveranumberofatoms
Someresonancestructurescontributemoretotheoverallstructurethanothers
Determiningwhichstructuresaremorecontributing
Structureswhereallatomshavefilledvalenceshells
Structureswiththegreaternumberofcovalentbonds
Structureswithlesscharges
Formalchargescanhelpdiscernwhichstructureismostlikely(discussedlaterinthissection)
Structuresthatcarryanegativechargeonthemoreelectronegativeatom
ExampleofResonanceStructures:
Curvedarrow–symbolusedtotheredistributionofvalenceelectrons
Alwaysdrawnasnotedinthefigurebelow
HowCurvedArrowsareDrawn:
FormalCharge
Anatom’sformalchargeis:
Totalnumberofvalenceelectrons
Minusallunsharedelectron
Minus½ofitssharedelectrons
Formalchargeshavetosumtotheactualchargeofthespecies
0chargeforamolecule
Ionicchargeforanion
Lewisstructureswiththesmallestformalchargearethemostlikelytooccur
FormalChargevs.OxidationNumber
Formalchargesareusedtoexamineresonancehybridstructures
Oxidationnumbersareusedtomonitorredoxreactions
Formalcharge
Bondingelectronsareassignedequallytotheatoms
Eachatomhashalftheelectronsmakingupthebond
FormalCharge=valencee-–(unbondede-+½bondinge-)
OxidationNumber
Bondingelectronsaretransferredcompletelytothemoreelectronegativeatom
OxidationNumber=valencee-–(unbondede-+bondinge-)
Valence-ShellElectronPairRepulsionModel(VSEPR)
VSEPRpredictstheshapesofmoleculesandionsbyassumingthatthevalenceshellelectronpairsarearrangedasfarfromoneanotheraspossible.
Moleculargeometry–3-Darrangementofatomsthatconstituteamolecule
Shapeofamoleculeisdeterminedbythepositionsofatomicnucleirelativetoeachother
Rulestohelpdiscernelectronpairarrangements
Selectthecentralatom
Placeatomwiththelowestgroupnumberinthecenter
Ifatomssharethesamegroupnumberplacetheatomwiththehigherperiodnumberinthecenter
DrawtheLewisstructure
Determinethenumberofbondingelectronpairsaroundthecentralatom
Determinethenumberofnon-bondingelectronpairs
Multiplebondsarecountedasasingleelectronpair
Arrangetheelectronpairsasfarapartaspossible
Minimizeselectronrepulsions
Addthenumberofbondingandlonepairs
Fromthatnumberandthenumberoflonepairsyoucanusethechartbelowtodeterminethegeometry
Forexample:Ifyouweregivenamoleculewherethecentralatomhad2bondingpairsand1non-bondingpair(totalnumber=3),themolecularshapewouldbebent/angular
ExampleQuestion:DeterminethemolecularshapeofCO2accordingtoVSEPRtheory.
CO2:
Centralatom:C
Chas2bondingpairs,0non-bondingpairs
Rememberthatdoublebondsarecountedasasingleelectronpair
AccordingtoVSEPRmodelthebondsarearrangedlinearly
Bondangle=180˚
Molecularshapeislinear
ExampleQuestion:DeterminethemolecularshapeofCOCl2accordingtoVSEPRtheory.
ExampleofCOCl2:
Centralatom:C
Chas3bondingpairs,0non-bondingpairs
AccordingtoVSEPRmodelthethreegroupsofelectronpairsarearrangedinatrigonalplane
Bondangle=120˚
Molecularshapeistrigonalplanar
EffectofLonePairs
Lonepairsarelessconfinedbecausetheyareheldbyasinglenucleus
Allowsthemtoexertastrongerrepulsiveforcethanabondingpair
Resultsinadecreaseintheanglebetweenbondingpairs
DipoleMomentDipolemoment(µ)-measureofthedegreeofchargeseparation(molecularpolarity)inamolecule
µ=Q*rQ=Charger=distancebetweenthecharges
Polarityofindividualbondswithinamoleculecanbeviewedasvectorquantities
Moleculesthatareperfectlysymmetrichaveazerodipolemoment
ThesemoleculesareconsiderednonpolarMoleculesthatexhibitanyasymmetryinthearrangementofelectronpairswillhavesomedipolemoment
Thesemoleculesareconsideredpolar
ExampleofH2OPolarityVectors:MolecularGeometryandDipoleMomentRelatedness
CHAPTER9–BONDINGTHEORIES
ValenceBondTheory
Valencebondtheoryisanattempttoexplainthecovalentbondfromaquantummechanicalview.
Orbitals(s,p,d,f)ofthesametypehavethesameenergy
Accordingtothetheory,abondformswhentwoatomicorbitalsoverlap
Spaceformedbyoverlappingorbitalshasacapacityfortwoelectrons
Musthaveoppositespins(+½and-½)
Eachorbitalformingthebondhasatleastoneunfilledslottoaccommodatetheelectronbeingshared
Bondstrengthdependsontheattractionofthenucleiforthesharedelectrons
Greaterorbitaloverlap=strongerbond
Overlapdependsontheshapesanddirectionoftheorbitals
HybridOrbitals
Quantummechanicalcalculationsshowthatifspecificcombinationsoforbitalsaremixed,“new”atomicorbitalsareformed
Theseneworbitalsarecalledhybridorbitals
Typesofhybridorbitals
Eachtypehasauniquegeometricarrangement
Hybridorbitalsareusedtodescribebondingthatisobtainedbytakingcombinationsofatomicorbitalsofanisolatedatom
Stepsfordeterminingbondingdescription
WritetheLewisdotformulaforthemolecule
ThenusetheVSEPRtheorytodeterminethearrangementofelectronpairsaroundthecentralatom
Fromthegeometricarrangement,determinethehybridizationtype
Assignvalenceelectronstothehybridorbitalsofthecentralatomoneatatime
Paironlywhennecessary
Formbondstothecentralatombyoverlappingsinglyoccupiedorbitalsofotheratomswiththesinglyoccupiedhybridorbitalsofthecentralatom
MultipleBonds
Orbitalscanoverlaptwoways
Sidetoside
Endtoend
Twotypesofcovalentbonds
Sigmabonds(C-C)
Formedfromanoverlapofoneendoftheorbitaltotheendofanotherorbital
pibonds(C=C)
Formedwhenorbitalsoverlapsidetoside
Createstworegionsofelectrondensity
Oneaboveandonebelow
Doublebondsalwaysconsistofonesigmabondandonepibond
MolecularOrbitalTheory
Asatomsapproacheachotherandtheiratomicorbitalsoverlap,molecularorbitalsareformed
Onlyouter(valence)atomicorbitalsinteractenoughtoformmolecularorbitals
Combiningatomicorbitalstoformmolecularorbitalsinvolvesaddingorsubtractingatomicwavefunctions
Addingwavefunctions
Formsabondingmolecularorbital
Electronchargebetweennucleiisdispersedoveralargerareathaninatomicorbitals
Molecularorbitalshavelowerenergythanatomicorbitals
Reductioninelectronrepulsion
Bondingmolecularorbitalismorestablethanatomicorbital
SubtractingWaveFunctions
Formsaantibondingmolecularorbital
Electronsdonotshieldonenucleifromtheother
Resultsinincreasednucleus-nucleusrepulsion
Antibondingmolecularorbitalshaveahigherenergythanthecorrespondingatomorbitals
Whentheantibondingorbitalisoccupied,themoleculeislessstablethanwhentheorbitalisnotoccupied
MolecularOrbitalsofH2:
CHAPTER10-GASESANDGASLAWS
PropertiesofGases
Flowfreely
Relativelylowdensities
Gasesformhomogenousmixtureswitheachother
Volumeofgaseschangesignificantlywithpressure
Volumesofsolidsandliquidsvolumesarenotgreatlyaffectedbypressure
Volumeofgaseschangessignificantlywithtemperature
Underhightemperaturesgasesexpand
Underlowtemperaturesgasescontract
Pressure
Force(F)-afunctionofthemassofanobjectunderacceleration
F=MassxAcceleration
Pressure(P)-forceexertedperunitareaofsurfacebymoleculesinmotion
A=area
m=mass
a=acceleration
d=density
g=accelerationduetogravity=9.81m/s2
h=heightofcolumn(m)
Pressurehasmanyunits
SIunitisPascal(Pa)=1kg•m-1•sec-2
Atmosphereandtorrarecommonlyused
1atmosphere(atm)=760mmHg=760torr
GasLaws
Thebehaviorofgascanbedescribedbypressure(P),temperature(T),volume(V),andmolaramount(n).Ifyouholdanyofthetwovariablesconstant,itallowsfordeterminationofarelationshipbetweentheothertwo.
Idealgas–gasthatexhibitslinearrelationshipsamongpressure,temperature,volume,andmolaramount
Idealgasesdon’tactuallyexist
Butsimplegasesbehaveideallyundernormaltemperaturesandpressures
Molargasvolume(Vm)–volumeofonemoleofgas
Volumesofgasesareoftencomparedatstandardtemperatureandpressure(STP)
StandardTemperature=0˚C(273K)
StandardPressure=1atm
VmatSTP=22.4L/mol
BoylesLaw
Volumeofasampleofgasataconstanttemperatureisinverselyrelatedtotheappliedpressure
P1V1=P2V2or
CharlesLaw
Volumeofasampleofgasatconstantpressureisdirectlyproportionaltotheabsolutetemperature
Avogadro’sLaw
Equalvolumesofdifferentgasesatthesametemperatureandpressurecontainequalnumberofparticles
CombinedGasLaw
ForwhenP,V,andTarechanging
IdealGasLaw
PV=nRT
Ristheuniversalgasconstant
R=0.082058L•atm•mol-1•K-1=8.3145J•mol-1•K-
1
Aslongasyouknowthreeofthevariablesyoucanmanipulatetheidealgaslawtosolveforthefourth
MolarMassfromIdealGasLaw
Density
LawofPartialPressures
Kinetic-MolecularTheoryofGases
Amodelbasedonactionsofindividualatoms
Gasesconsistofparticlesinconstantmotion
Pressurederivedfrombombardmentwithcontainer
Kineticenergyformula:Ek=½mv2
PostulatesofKineticTheory
Volumeofparticlesisnegligible
Particlesareinconstantmotion
Noinherentattractiveorrepulsiveforces
Theaveragekineticenergyofacollectionofparticlesisproportionaltothetemperature(K)
MolecularMotioninGases
Diffusion–transferofgasthroughspaceoranothergasovertime
Effusion–transferofagasfromaregionofhighpressuretoaregionoflowpressure
GrahamsLawofEffusion
CHAPTER11-THERMOCHEMISTRY
Thermochemistry
Inchemicalreactionswhenevermatterchangescomposition,itsenergycontentchangesaswell
Insomereactionstheenergycontainedinthereactantsishigherthantheenergycontainedintheproducts
Theexcessenergyisreleasedasheat
Inotherreactionstheenergycontainedinthereactantsislowerthantheenergycontainedintheproducts
Inthesereactions,energy(heat)mustbeaddedbeforethereactioncanproceed
Physicalchangesalsoinvolveachangeinenergy
Thermodynamics-scienceoftherelationshipbetweenheatandotherformsofenergy
Thermochemistry-studyofthequantityofheatabsorbedorexudedbychemicalreactions
Energy
Energyisthepotentialorcapacitytodowork.Energyisapropertyofmatterandcomesinmanyforms.
Formsofenergy
Radiantenergy-electromagneticradiation
Thermalenergy-associatedwithrandommotionofamoleculeoratom
Chemicalenergy-energystoredwithinthestructurallimitsofamoleculeoratom
ConceptsofEnergy
Kineticenergy(Ek)–energypossessedbyanobjectduetoitsmotion
Ek=½mv2
Potentialenergy(Ep)–energystoredinmatterbecauseofitspositionorlocation
Ep=mgh
Internalenergy(EiorUi)–energyassociatedwiththerandomdisorderedmotionofmolecules
Ei=Ek+Ep
UnitsofEnergy
SIunitofenergyistheJoule(J)=kg•m2/s2
Calorie(cal)-amountofheatrequiredtoraisethetemperatureofonegramofwaterbyonedegreeCelsius
1cal=4.181J
Whenreactantsinteracttoformproductsandtheproductsareallowedtoreturntothestartingtemperature,theInternalEnergy(E)haschanged
∆E=changeinenergy
∆isthesymbolforchange
∆=finalvalue–initialvalue
∆E=Efinal-Einitial=Eproducts-Ereactants
Ifenergyislosttothesurroundings
Efinal<Einitial
∆E<0
Ifenergyisgainedfromthesurroundings
Efinal>Einitial
∆E>0
HeatofReaction
Inchemicalreactions,heatiseithertransferredfromthe“system”toits“surroundings,”orviceversa.
Thermodynamicsystem-quantityofmatterorthespaceunderthermodynamicstudy
Surroundings-everythinginthevicinityofthethermodynamicsystemthatinteractswiththesystem
Heat(q)-energythatflowsintooroutofasystembecauseofadifferenceintemperaturebetweenthesystemanditssurroundings
Heatflowsfromaregionofhighertemperaturetoaregionoflowertemperature
Oncetemperaturesequalize,heatflowstops
Whenheatisreleasedfromthesystemtothesurrounding
q<0
Reactioniscalledanexothermicreaction
Whenheatisabsorbedfromthesurroundingbythesystem
q>0
Reactioniscalledanendothermicreaction
Heatofreaction-thevalueof“q”requiredtoreturnasystemtoagiventemperaturewhenthereactiongoestocompletion
Work
Internalenergyisspecificallydefinedasthecapacityofasystemtodowork.
Work–energytransferredwhenanobjectismovedbyaforce
w=-P∆V
∆E=qp+w
∆E=qp+-P∆V
qp=∆E+P∆V
qp-heatabsorbedfromthesurroundingsbythesystem
∆E-changeininternalenergy
∆V-changeinvolume
P–pressure
EnthalpyandEnthalpyChange
Enthalpy(H)-anextensivepropertyofasubstancethatisusedtoobtaintheheatabsorbedorexudedinachemicalreaction
H=E+PV
Enthalpyisastatefunction
Propertyofasystemthatdependsonlyonitsstateatthemomentandisindependentofanyhistoryofthesystem
Enthalpyisrepresentativeoftheheatenergytiedupinchemicalbonds
Changeinenthalpy(∆H)-heataddedorlostbythesystem,underconstantpressure
∆H=∆E+P∆V
∆H=qp
Changeinenthalpyisalsocalledtheenthalpyofreaction
∆Hrxn=H(products)–H(reactants)
Ifthesystemhashigherenthalpyattheendofthereaction
Itabsorbedheatfromthesurroundings
Itisanendothermicreaction
Hfinal>Hinitial
∆Hispositive(+∆H)
Ifthesystemhaslowerenthalpyattheendofthereaction
Itexudedheattothesurroundings
Itisanexothermicreaction
Hfinal<Hinitial
∆Hisnegative(-∆H)
ThermochemicalEquation
Thermochemicalequationsarechemicalreactionequationswiththeenthalpyofreaction(∆Hrxn)writtendirectlyaftertheequation.
Exampleofathermochemicalequation
2H2(g)+O2(g)→2H2O(l)∆Hrxn=-571.6kJ
Thenegativevaluefor∆Hrxnistellingyouthatheatislosttothesurrounding
Alsothattheequationisexothermic
Rulesformanipulatingthermochemicalequations
Ifthethermochemicalequationismultipliedbysomefactor,thevalueof∆Hforthenewequationisequaltothe∆Hintheoriginalequationmultipliedbythatfactor
Ifthechemicalequationisreversed,thesignof∆Hmustbereversed
Example,ifyouweretoreversethedirectionoftheequationmentionedaboveyouwouldget:
2H2O(l)→2H2(g)+O2(g)∆Hrxn=+571.6kJ
MeasuringHeatsofReaction
Heatcapacity–amountofheatrequiredtoraisethetemperatureofanobjectorsubstance
Variesbetweensubstances
Molarheatcapacity(C)–amountofheatrequiredtoraisethetemperatureofonemoleofasubstancebyonedegreeCelsius
q=nC∆T
∆T=Tfinal-Tinitial
Specificheatcapacity(S)–amountofheatrequiredtoraisethetemperatureofonegramofasubstancebyonedegreeCelsius
q=mS∆T
∆T=Tfinal-Tinitial
UnitsforS:J/g•˚C
m=gramsofasample
Hess’sLawofHeatSummation
Forachemicalequationthatcanbewrittenasthesumoftwoormoresteps,theenthalpychangesfortheindividualstepscanbesummed(added)uptodeterminetheenthalpychangefortheoverallequation
Forcoupledreactions,theindividualenthalpychangescanbesummeduptodeterminetheenthalpychangefortheoverallreaction
Hess’sLawExampleQuestion:Whatisthestandardenthalpyofreactionforthereductionofiron(II)oxidebycarbonmonoxide?FeO(s)+CO(g)→Fe(s)+CO2(g)
GivenInformation:
Equation1:3Fe2O3(s)+CO(g)→2Fe3O4(s)+CO2(g)ΔH=-48.26kJ
Equation2:Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g)ΔH=-23.44kJ
Equation3:Fe3O4(s)+CO(g)→3FeO(s)+CO2(g)ΔH=+21.79kJ
Changeshavetomadetotheaboveequationstoequaltheequationinthequestion
Reverseequation3andmultiplyitbytwo
PutsFeOonthereactantsideandmoves2Fe3O4totheproducts
Reverseequation1
PutsFe3O4onoppositesidetocancelwiththereverseofequation3
Multiplyequation2bythree
Gives3Fe2O3onthereactantsthatwillbeusedtocancel
Newequationsafterchanges
Equation1:2Fe3O4(s)+CO2(g)→3Fe2O3(s)+CO(g)ΔH=+48.26kJ
Equation2:3Fe2O3(s)+9CO(g)→6Fe(s)+9CO2(g)ΔH=-70.32kJ
Equation3:6FeO(s)+2CO2(g)→2Fe3O4(s)+2CO(g)ΔH=-43.58kJ
Summingthethreeequationsgives
6FeO(s)+6CO(g)→6Fe(s)+6CO2(g)ΔH=-65.64kJ
Dividingbysixgivestheequationinthequestionandthefinalanswer
FeO(s)+CO(g)→Fe(s)+CO2(g)ΔH=-10.94kJ
StandardEnthalpiesofFormation
Standardstatereferstothestandardthermodynamicconditions
Pressure-1atm(760mmHg)
Temperature-25˚C(298K)
Enthalpychangeforareactionwherereactantsareintheirstandardstatesiscalledthe“StandardHeatofReaction”
ΔH˚rxn
Standardenthalpyofformationofasubstance-enthalpychangefortheformationofonemoleofasubstanceinitsstandardstatefromitscomponentelementsintheirstandardstates
Standardenthalpyofformationfora“pure”element(C,Fe,O,N,etc.)initsstandardstateiszero
LawofSummationofHeatsofFormation
Thestandardheatofreaction(∆H˚rxn)isequaltothetotalformationenergyoftheproductsminusthetotalformationenergyofthereactants
mandnarecoefficientsofthesubstancesinthechemicalequation
GibbsFreeEnergyGibbsfreeenergycanbeusedtodeterminethedirectionofthechemicalreactionundergivenconditions .
∆G=∆H-T∆Sor∆G=Gproducts-Greactants
G=Gibbsfreeenergy(J/mol)
H=enthalpy(J/mol)-totalenergycontentofasystem
S=entropy(J/K*mol)-measureofdisorderorrandomness(howenergyisdispersed)
T=Temperature(K)
AsTincreasessodoesS
+∆Gmeansenergymustbeputintothesystem
Indicatesthataprocessisnonspontaneousorendergonic
Indicatesthatthepositionoftheequilibriumforareactionfavorstheproducts
-∆Gmeansenergyisreleasedbythesystem
Indicatesthataprocessisspontaneousorexergonic
Indicatesthatthepositionoftheequilibriumforareactionfavorsthereactants
∆G=0indicatesthatthesystemisatequilibrium
Important:∆Gonlyindicatesifaprocessoccursspontaneouslyornot,butdoesnotindicateanythingabouthowfastaprocessoccurs.
CHAPTER12:SOLUTIONS
Solutions
Solutionsarecomposedofasoluteandasolvent
Solutionsarehomogeneousmixtures
Solutesareminorcomponentsinasolution(presentinsmalleramounts)
Solventsaresubstancesinwhichasoluteisdissolved
Solutioncompositionisexpressedby:
Masspercent
Molefraction
Xsolute
Xsolute=nsolute/ntotal
Molarity
Molality
ConversionbetweenMolarityandMolality
Densitymustbeknowntoconvertfrommolaritytomolalitydirectly.
ExampleQuestion:Whatismolalityof2.00MNaCl(aq)solutionwithadensityof1.08g/mL?
Determinethemassof2.00molofNaCl
2.00molx(58.5g/mol)=117gNaCl
Assumeyouhave1.000L(1000mL)ofthe2.00MNaClsolution
Youcanassumeanyamountifitisnotexplicitlystatedinthequestion
Hint:itisbesttoassumeanamountthatiseasytoworkwith
Toconvertmolaritytomolalityassume1.000Lofsolution
Toconvertmolalitytomolarityassume1.000kgofsolvent
Usethedensitygivenintheproblemtodeterminethetotalmassofthesolution
1000mLx(1.08g/mL)=1080gtotalmass
Determinethemassofthesolvent
Earlierwecalculatedthatwehad117gNaClandthetotalmassofthesolutionwas1080g
So,todeterminethemassofthesolventwewillsimplysubtractthedifference
1080gofsolution–117gNaCl=963gsolvent(0.963kgsolvent)
Finally,usetheformulaformolalitytodeterminetheanswer
Concentratedvs.DiluteSolutions
Concentratedsolution–asolutionthatcontainsahighamountofsolute
Moresoluteparticlesperunitvolume
Dilutesolution–asolutionthatcontainsalowamountofsolute
Fewersoluteparticlesperunitvolume
Saturatedsolution-asolutionthatcontainsthemaximumamountofsolutethatcanbedissolvedbythesolvent
Dilutions
Extrasolventisaddedtoasolutiontodiluteit
Theamountofsoluteinthesolutionremainsthesame
Usethefollowingformulatosolvedilutionproblems:
M1V1=M2V2
M1–istheconcentrationofstocksolution
V1–isthevolumeofstocksolution
M2–istheconcentrationofthefinalsolution
V2–isthevolumeofthefinalsolution
Henry’sLaw
FormulatedbyWilliamHenryin1803,itstates:"Ataconstanttemperature,theamountofagivengasthatdissolvesinagiventypeandvolumeofliquidisdirectlyproportionaltothepartialpressureofthatgasinequilibriumwiththatliquid."
C=kxPgas
C–solubilityofagasatafixedtemperatureinaparticularsolvent
k-Henry’sLawconstant
Pgas–partialpressureofthegas
ColligativeProperties
Colligativepropertiesrefertopropertiesofsolutionsthatdependupontheratioofthenumberofsoluteparticlestothenumberofsolventmoleculesinasolution.Thesepropertiesdon’tdependonthetypeofchemicalspeciespresent.
Commoncolligativeproperties
Vaporpressurelowering
Freezingpointdepression
Boilingpointelevation
Osmoticpressure(discussedindetailinitsownsection)
VaporPressureLowering
Raoult’sLawsaysthatifyouaddanonvolatilesolutetoasolvent,youwillcausethevaporpressureofthesolutetobelower
Raoult’sLawequation:
Psolution=XsolventPosolvent
Psolution-vaporpressureofsolution
Xsolvent-molefractionofsolventinsolution
Posolvent-vaporpressureofpuresolvent
BecauseXsolventisamolefraction(anumberbetween0and1),PsolutionisalwayslowerthanPosolvent
FreezingPointDepression
Propertybasedontheobservationthatfreezingpointsofsolutionsarealllowerthanthatofthepuresolventandisdirectlyproportionaltothemolalityofthesolute
Formula:∆Tf=Tf(solvent)-Tf(solution)=Kfxm
∆Tf-freezingpointdepression
Tf(solvent)–freezingpointofthesolvent
Tf(solution)–freezingpointofthesolution
Kf=freezingpointdepressionconstant
m–molality
BoilingPointElevation
Propertybasedontheobservationthattheboilingpointofasolventishigherwhenanothercompoundisadded(i.e.solutionhasahigherboilingpointthanapuresolvent)
Formula:∆Tb=Kbxm
∆Tb–boilingpointelevation
Kb=boilingpointelevationconstant
m–molality
OsmoticPressure
Semipermeablemembranesstopsolutemoleculesorionsfrompassingthroughbutallowpassageofsolventmolecules.Solventmoleculessuchaswaterwillgothroughmembranestodiluteasolutionunlessapressureequaltotheosmoticpressureisappliedtostoptheflow.So,osmoticpressureisdefinedastheminimumpressurewhichneedstobeappliedtoasolutiontopreventtheinwardflowofwateracrossasemipermeablemembrane.
Hypertonic-referstoasolutionthathashigherosmoticpressurethanaparticularfluid(e.g.intracellularfluid)
Isotonic-referstoasolutionthathasthesameosmoticpressurethanaparticularfluid(e.g.intracellularfluid)
Hypotonic-referstoasolutionthathasthelowerosmoticpressurethanaparticularfluid(e.g.intracellularfluid)
Osmoticpressure( )formula
V=nRTor =MRT
n=molesofsolute
V=volumeofsolution(L)
R=gasconstant(0.08206L · atm/mol ·K)
T=temperatureinKelvin
M=molarity
HydrophobicEffectandAmphiphilicMoleculesThehydrophobiceffectisthetendencyofnonpolarsubstancestoaggregateinaqueoussolutionandexcludewatermolecules.Amphiphilicmoleculeshavebothhydrophobicandhydrophilicparts.
Hydrophobic–water“hating”Incontrast,hydrophilic–water“loving”
AmphiphilicMoleculesinWater
Nonpolartails(hydrophobicportion)pointawayfromwaterPolarheads(hydrophilicportion)areexposedtowater
DifferentamphipathicmoleculesaggregateindifferentwaysbasedonthenumberoftailsandsizeofthepolarheadgroupMicellesformwhenthereisonly1tailandtakesphericalforminaqueoussolutions
CHAPTER13–CHEMICALKINETICS
Introduction
Reactionsoccuratdifferentrates
Someareveryquick,someareveryslow,andmanyfallsomewhereinbetween
Knowingtherateofareactionhelpschemistsplanoutexperimentsandplanreactionsaccordingly
Ifyouunderstandwhatcontributestorate,youcanexertsomecontroloverareaction
Chemicalequations(e.g.,Al2O3→Al+O2)don’ttellyouanythingabouthowfastthereactionoccurs
Somereactionsoccurinaseriesofsmallerstepsthatleadtothefinalproduct
ReactionRates
Generally,ratesaredefinedasthechangeofsomethingdividedbychangeintime.Thisistrueofreactionratesaswell.
Rateofareactioncanbewrittenwithrespecttoanycompoundinthatreaction
But,therecanonlybeonenumericalvalueforarateofreaction
Ifyouplotaverageratedataasafunctionoftime,youwillseethatthereactionrateconstantlychanges(considerthegraphbelow)
RateDataforaReaction:
Asyoumightnotice,ratedependsontheconcentrationofthereactants
Sincetherateofareactioniseffectedbytheconcentrationofthereactantswecanwritemathematicalrelationshipslinkingtheconcentrationofreactantswithhowfastthereactionoccurs(i.e.wecanwriteratelaws)
GeneralReactionRates
Considerthegeneralchemicalequation:aA+bB→cC+dD
Rateforthisreactionwouldbedefinedas:
Asimpleratelawexample:
Considerthedecompositionreactionwhere:A products
Ifthereversereactionisnegligible,thentheratelawis:Rate=k[A]n
kiscalledtherateconstant
niscalledthereactionorder
ReactionOrders
Reactionorder(denotedas“n”)determineshowtheratedependsontheconcentrationofthereactant
n=0,zeroorder,rateisindependentof[A]
n=1,firstorder,rateisdirectlyproportionalto[A]
n=2,secondorder,rateisproportionaltothesquareof[A]
Eachorderresultsinadifferenttypeofcurvewhengraphed
Important:Youcanonlydeterminereactionordersthroughanexperiment
Reactionordersarenotrelatedtothestoichiometryofareaction
StepsforFindingRateLaw
Picktwosolutionswhereonereactantstayssame,butanotherchanges
Writetheratelawforbothusingasmuchinformationasyouhave
Formaratiofromthetwoandsolveforanorder
Repeatthe3stepsaboveforanotherpairofsolutions
Useanyreactiontogetthevalueofk
AnExampleProblem
Imagineweareconsideringthegeneralreaction:A+B→products
Andthatwedeterminedthefollowinginformationfromanexperiment:
Lookatexperiments1and2
Fromexperiment2to1,weseethattheconcentrationofAdoubles(whileBisheldconstant)andtheratealsodoubles
DoublingoftheratewithadoublingoftheconcentrationshowsthatthereactionisfirstorderwithrespecttoA
Nextlookatexperiments1and3
ConcentrationofBishalved(whileAisheldconstant)
WhenBishalved,theoverallratedropsbyafactorof4(whichisthesquareof2)
ThisshowsthereactionissecondorderwithrespecttoB
Theratelawwouldbewrittenas:rate=k[A][B]2
Youcanuseanyreactiontogetthevalueofk(Iwilluseexperiment1)
Rate=k[A][B]2
1.60mMmin-1=k(4.0mM)(6.0mM)2
k=0.011mM-2min-2
IntegratedRateLawandHalfLifeFormulas
Notethattheintegratedratelawequationsareintheformy=mx+b
y=mx+bistheformulaforastraightline
So,theplotofln[A]vs.timeforthereactionswillyieldastraightline
For2ndorder,half-lifedependsoninitialconcentration
Asconcentrationdecreases,thehalf-lifeincreases
Half-lifeforzeroorderreactionsdependsonconcentrationaswell
However,noticethatthehalf-lifedoesn’tdependonreactantconcentrationforthe1storderreactions
Half-lifefora1storderreactionisconstant
TemperatureandRateGenerally,ratesofreactionaresensitivetotemperature
Rate=k[A]n,sowheredowefactorintemperature?ItisreflectedintheconstantkGenerally,increasingtemperatureincreasesk
ChemistryofCatalysisCatalystsdonotchangethedirectionofachemicalreactionandtheyhavenoeffectonequilibrium!
Functionbyloweringtheactivationenergy,whichspeedsupthereaction
Asthereactionprogresses;reactantsbecomeproducts
Depictedasareactioncoordinatediagram
ReactionCoordinateDiagram:
Progressofthereactionisindicatedonthex-axis
Freeenergy(G)isindicatedonthey-axis
Reactantspassthroughthetransitionstate(‡)andbecomeproducts
Enzymesincreasethereactionratebybindingtightlytothetransitionstateandstabilizingit
Spontaneousvs.Non-spontaneousReactionsSpontaneousifΔGrxnnegative
GeneralSpontaneousReactionDiagram:
Non-spontaneousifΔGrxnpositive
GeneralNon-spontaneousReactionDiagram:
Enzymes(catalysts)lowertheenergybarrierMakeiteasiertoreachthetransitionstate
CHAPTER14–CHEMICALEQUILIBRIUM
WhatisEquilibrium?
Asasystemisapproachingequilibrium,boththeforwardandreversereactionsareoccurringatdifferentrates
Chemicalequilibriumisestablishedwhenareactionanditsreversereactionoccuratthesamerate
Onceequilibriumisestablished,theamountofboththereactantandproductremainsconstant
Inasystematequilibrium,boththeforwardandreversereactionsarerunningsimultaneouslysowewritethechemicalequationforthereactionwithadoublearrow
Example:
EquilibriumConstant
Considerthereaction:
Ratelawfortheforwardreactionwouldbe:rate=kf[N2O4]
Ratelawforthereversereactionwouldbe:rate=kr[NO2]2
Atequilibriumthetworateswouldbethesamesowecanrearrangetheequationstoget:
Keq(akaKc)istheequilibriumconstant
Ingeneral,thereaction:
Resultsintheequilibriumexpression:
Equilibriumcanbereachedfromeithertheforwardorreversedirection
Kc,thefinalratioof[NO2]2to[N2O4],willreachaconstantnomatterwhattheinitialconcentrationsofNO2andN2O4
are(aslongastimeisheldconstantbetweenthem)
Alsonotethattheequilibriumconstantofareactioninthereversereactionisthereciprocaloftheequilibriumconstantoftheforwardreaction
IfK>>1,thereactionissaidtobeproduct-favored
Productspredominateatequilibrium
IfK<<1,thereactionissaidtobereactant-favored
Reactantspredominateatequilibrium
Ifareactionconsistsofmanyindividualsteps,youcanaddtheequilibriumconstantsfortheindividualstepstodeterminetheequilibriumconstantfortheentirereaction
Pressureisproportionaltoconcentrationforgases,becauseofthis,theequilibriumexpressioncanalsobewrittenintermsofpartialpressures(insteadofconcentration)
KpandKcarerelatedtooneanotherbytheequation:Kp=Kc(RT)∆n
∆n=(molesofgaseousproduct)–(molesofgaseousreactant)
HomogeneousandHeterogeneousEquilibrium
Ahomogeneousequilibriumisanequilibriumwhereallreagentsandproductsarefoundinthesamephase(solid,liquid,orgas).Aheterogeneousequilibriumisanequilibriumwheretheyareindifferentphases.
Concentrationsofliquidsandsolidscanbeobtainedbythefollowing:
Concentrationofsolidsandliquidsarenotusedtoformanequilibriumexpression
Considerthereaction:
Theequilibriumconstantforthereactionwouldbe:
Kc=[Pb2+][Cl−]2
ReactionQuotient(Q)
TocalculateQ,youhavetosubstitutetheinitialconcentrationsofreactantsandproductsintotheequilibriumexpression
Qgivesthesameratioastheequilibriumexpressionbutforasystemthatisnotatequilibrium
IfQ=K,thesystemisatequilibrium
IfQ>K,thereismoreproduct,andtheequilibriumshiftstothereactants
IfQ<K,therearemorereactants,andtheequilibriumshiftstotheproducts
TheshiftingofequilibriumisLeChâtelier’sPrinciple
Essentiallytheprinciplestatesthatequilibriumpositionshiftstocounteracttheeffectofadisturbance(changeintemperature,concentration,etc.)
CHAPTER15–ACIDBASEEQUILIBRIUM
DefinitionsandConventions
Acid-basereactionsareatypeofchemicalprocesstypifiedbytheexchangeofoneormorehydrogenions(i.e.exchange/transferofaproton).
Arrheniusdefinition
Acid–substancethatproducesH+ionsinaqueoussolution
WenowknowthatH+reactsimmediatelywithawatermoleculetoproduceahydroniumion(H3O+)
Base–substancethatproducesOH-ionsinaqueoussolution
Bronsted-Lowrydefinition
Acid–protondonor
Base–protonacceptor
Bronsted-Lowrydefinitiondoesnotrequirewaterasareactant
Conjugateacidsandbases
Conjugatebase–speciesthatisformedwhenanaciddonatesaprotontoabase
Conjugateacid–speciesthatisformedwhenabaseacceptsaprotonfromanacid
Conjugateacid-basepair–pairofmoleculesorionsthatcanbeinterconvertedthroughthetransferofaproton
Curvedarrowsareusedtoshowtheflowofelectronsinanacid-basereaction
NeutralizationisthereactionofanH+(H3O+)ionfromtheacidandtheOH-ionfromthebasetoformwater,H2O
Neutralizationreactionisexothermicandreleasesapproximately56kJpermoleofacidandbase
Determiningacidic,basic,andneutralfromconcentrationofH3O+
andOH-
Neutral:[H3O+]=[OH-]
Acidic:[H3O+]>[OH-]
Basic:[H3O+]<[OH-]
StrengthsofAcidsandBases
Strengthofanacidisexpressedbyanequilibriumconstant
Equilibriumexpressionforthedissociationofanunchargedacid(HA)
Ka,theaciddissociationconstant,isgivenby:
Thisisbecausetheconcentrationofwaterishigh,anddoesnotsignificantlychangeduringthereaction,soitsvalueisabsorbedintotheconstant
Thestrongertheacid,thelargertheKa,andthemoreitwilldissociateinsolution
Strongacidscompletelydissociateintoionsinwater
StrongacidsareHI,HBr,HClO4,HCl,HClO3,H2SO4,andHNO3
Theirconjugatebasesareweak
Weakacidsonlypartiallydissociateintoionsinwater
Polyproticacidsareacidsthatarecapableoflosingmorethanasingleprotonpermoleculeduringanacid-basereaction
Phosphoricacidisaweakacidthatnormallyonlylosesoneprotonbutitwillloseallthreewhenreactedwithastrong
baseathightemperatures
IfthedifferencebetweentheKaforthefirstdissociationandsubsequentKavaluesis103ormore,thepHgenerallydependsonlyonthefirstdissociation
Inanyacid-basereaction,theequilibriumfavorsthereactionthatmovestheprotontothestrongerbase
ThemorepolartheH-Xbondand/ortheweakertheH-Xbond,themoreacidicthecompound
Strongbase–abasethatispresentalmostentirelyasions(oneoftheionsisOH-)
StrongbasesareNaOH,KOH,LiOH,RbOH,CsOH,Ca(OH)2,Ba(OH)2,andSr(OH)2
Weakbase–abasethatonlypartiallyionizesinwater
Thegeneralweakbasereactioniswrittenas:
Theequilibriumconstantexpressionforthisreactionis:
Kbiscalledthebase-dissociationconstant
KaandKbcanberelatedtooneanotherusingthefollowingformula:
KaxKb=Kw
Kwistheionizationconstantforwaterat25˚C
Kforwateris: or=1.0x10-14
FindingConcentrationofSpeciesinSolutionfromKa
Given:0.10MHNO2(nitrousacid),Ka=4.5x10-4
Setupatabletohelpyoukeeptrackofwhatishappeningduringthereaction
Someofthereactantwillbecomeproduct,thatiswhythechangeinconcentrationisnegativex
Weareformingsomeamountofproductinthisreactionsothechangeinconcentrationispositivex
Wenowneedtosolveforx,firstsetuptheKaequation
Thesimpleapproach:
ItisacceptedthataslongasX<5%of[HA],where[HA]=concentrationoftheacid,youcanassumexisnegligibleandthat(0.10-x)=0.10,makingtheKaequation:
Theexactapproach(quadraticformula):
However,ifyoucan’tassumexisgoingtobesmallerthan5%youhavetosetuptheexactformula
Thequadraticequationis:ax2+bx+c=0
→x2+4.5x10-4x–4.5x10-5=0
a=1
b=4.5x10-4
c=-4.5x10-5
Thequadraticformula:
Tosolve,substituteinthevaluesfora,b,andc
x=6.5x10-3
Alwaysuseonlythepositiveroot,thenegativerootdoesnotmakesenseinthecontextofthesesortofproblems
Ifyoucomparetheanswerfrombothapproaches(6.7x10-3vs.6.5x10-3)youcanseethattheanswersareprettymuch
thesame
However,rememberthatyoucanonlyusethesimpleapproachifX<5%of[HA]
Sincewefoundx,weonlyneedtosubstitutethevalueintothe“EquilibriumAmount”sectionofthetablewesetupearliertofindtheconcentrationofspeciesinsolution
[HNO2]=(0.10M–x)=(0.10M–6.5x10-3)=0.0935M
[H+]=x=6.5x10-3M
[NO2-]=x=6.5x10-3M
pHandpOH
pHisdefinedasthenegative,base-10logarithmofthehydroniumionconcentration
pH=-log[H3O+]→[H3O+]=10-pH
Inpurewater:
Kw=[H3O+][OH–]=1.0x10-14
Becauseinpurewater[H3O+]=[OH-];
[H3O+]=(1.0 10-14)1/2=1.0x10-7
pH=-log[1.0x10-7]=7.00
7.00isconsideredneutralpH
Anacidhasahigher[H3O+]thanpurewater
pHis<7
Abasehasalower[H3O+]thanpurewater
pHis>7
pHScalewithCommonSubstances:
pinpHisacluetotakethenegativelogofthequantity,thisistrueforpOHandpKw:
pOH=-log[OH-]→[OH-]=10-pOH
pKw=-log(Kw)→Kw=10-pKw
pKaandTrends
Ka=10-pka
pKa=-log(Ka)
LowerthepKa,thestrongertheacid
HigherthepKa,theweakertheacid
LowerthepKa,theweakertheconjugatebase
HigherthepKa,thestrongertheconjugatebase
Equilibriumfavorsthesideoftheweakestacidandweakestbase
EquilibriumfavorsthesidewiththehighestpKa
Thus,pKacanbeusedtopredictinwhichdirectionequilibriumlies
PercentIonizationFormulas
ReactionsofAnionsandCationswithWater
Anionsarebases
TheycanreactwithwaterinahydrolysisreactiontoformOH–
andtheconjugateacid:
Cationswithacidicprotons(likeNH4+)lowerthepHofasolution
becausetheyreleaseH+ionsinsolution
MostmetalcationsthatarehydratedinsolutionalsolowerthepHofthesolution
ActbyassociatingwithH2OandmakingitreleaseH+
Attractionbetweennonbondingelectronsonoxygenandthemetalcausesashiftoftheelectrondensityinwater
ThismakestheO-Hbondmorepolarandthewatermoreacidic
Greaterchargeandsmallersizemakeacationmoreacidic
EffectsofCationsandAnions
AnanionthatistheconjugatebaseofastrongacidwillnotaffectthepH
AnanionthatistheconjugatebaseofaweakacidwillincreasethepH
AcationthatistheconjugateacidofaweakbasewilldecreasethepH
CationsofastrongArrheniusbasewillnotaffectthepH
OthermetalionswillcauseadecreaseinpH
Whenasolutioncontainsboththeconjugatebaseofaweakacidandtheconjugateacidofaweakbase,theeffectonpHdependsontheKaandKbvalues
CHAPTER16–SOLUBILITYEQUILIBRIUM
WhatisSolubilityEquilibrium?
Ifan“insoluble”orslightlysolublematerialisplacedinwateranequilibriumformsbetweentheundissolvedsolidsandionicspeciesinsolutions
Solidscontinuetodissolve,whileion-pairscontinuetoformsolids
Therateofdissolutionisequaltotherateofprecipitation
Considerthereaction:AgCl(s)⇌ Ag+(aq)+Cl-(aq)
K=
However,rememberthatsinceAgClisapuresoliditisn’tconsideredinKandthustheequationcanberewrittenas:Ksp=[Ag+][Cl-]
SolubilityProduct(Ksp)
Generalexpression:MmXn(s)⇄ mMn+(aq)+nXm-(aq)
Solubilityproductforthegeneralexpression:Ksp=[Mn+]m[Xm-]n
Exampleofhowtofindsolubility(s)fromKsp:
AgCl(s)⇌ Ag+(aq)+Cl-(aq)
Ksp=[Ag+][Cl-]=1.6x10-10
IfsisthesolubilityofAgCl,then:
[Ag+]=sand[Cl-]=s
Ksp=(s)(s)=s2=1.6x10-10
s=1.3x10-5mol/L
Anotherexample:
Ag3PO4(s)⇌ 3Ag+(aq)+PO43-(aq)
Ksp=[Ag+]3[PO43-]=1.8x10-18
IfthesolubilityofAg3PO4issmol/L,then:
Ksp=(3s)3(s)=27s4=1.8x10-18
s=1.6x10-5mol/L
FactorsAffectingSolubility
Temperature
Generally,solubilityincreaseswithtemperature
Commonioneffect
Commonionsreducesolubility
Considerthefollowingsolubilityequilibrium:
AgCl(s)⇌ Ag+(aq)+Cl-(aq);Ksp=1.6x10-10
ThesolubilityofAgClis1.3x10-5mol/Lat25˚C.
IfNaClisadded,equilibriumshiftsleftduetoincreasein[Cl-]andsomeAgClwillprecipitateout
Forexample,if[Cl-]=1.0x10-2M,
SolubilityofAgCl=(1.6x10-10)/(1.0x10-2)=1.6x10-8mol/L
pHofsolution
pHaffectsthesolubilityofioniccompoundsinwhichtheanionsareconjugatebasesofweakacids
Considerthefollowingequilibrium:
Ag3PO4(s)⇌ 3Ag+(aq)+PO43-(aq);
IfHNO3isadded,thefollowingreactionoccurs:
H3O+(aq)+PO43-(aq)⇌ HPO4
2-(aq)+H2O
ThisreactionreducesPO43—insolution,causingmoresolid
Ag3PO4todissolve
Formationofcomplexion
Formationofcomplexionincreasessolubility
Manytransitionmetalsionshavestrongaffinityforligandstoformcomplexions
Ligandsaremoleculessuchas:H2O,NH3andCO,oranions,suchasF-,CN-andS2O3
2-
Complexionsaresoluble
Sotheformationofcomplexionsincreasessolubilityofslightlysolubleioniccompounds
PredictingFormationofPrecipitate
Qsp=Ksp
Saturatedsolution,butnoprecipitate
Qsp>Ksp
Saturatedsolution,withprecipitate
Qsp<Ksp
Unsaturatedsolution
QspisionproductexpressedinthesamewayasKspforaparticularsystem
ExampleQuestion:20.0mLof0.025MPb(NO3)2isaddedto30.0mLof0.10MNaCl.PredictifprecipitateofPbCl2willform.Given:KspforPbCl2=1.6x10-5
[Pb2+]=(20.0mLx0.025M)/(50.0mL)=0.010M
[Cl-]=(30.0mLx0.10M)/(50.0mL)=0.060M
Qsp=[Pb2+][Cl-]2=(0.010M)(0.060M)2=3.6x10-5
Qsp>Ksp,soPbCl2willprecipitate
CHAPTER17–ELECTROCHEMISTRY
WhatisElectrochemistry?
Electrochemistryisabranchofchemistryconcernedwiththestudyoftherelationshipbetweenelectronflowandredoxreactions.
Review:
Oxidation-reductionreactions(akaredoxreactions)–reactionsthatinvolveapartialorcompletetransferofelectronsfromonereactanttoanother
Oxidation=lossofelectrons
Reduction=gainofelectrons
Trickforrememberingwhichiswhich-OILRIG
OIL-OxidationIsLosingelectrons
RIG-ReductionIsGainingelectrons
Oxidationandreductionalwaysoccursimultaneously
OxidationNumber=valencee-–(unbondede-+bondinge-)
Oxidizingagent–speciesthatoxidizesanotherspecies
Itisitselfreduced–gainselectrons
Reducingagent–speciesthatreducesanotherspecies
Itisitselfoxidized–loseselectrons
ReducingandOxidizingAgents:
Oxidationnumber(akaoxidationstate)–actualchargeanatominamoleculewouldhaveifalltheelectronsitwassharingweretransferredcompletely,notshared
FormalChargevs.OxidationNumber
Formalchargesareusedtoexamineresonancehybridstructures
Oxidationnumbersareusedtomonitorredoxreactions
FormalCharge
Bondingelectronsareassignedequallytotheatoms
Eachatomhashalftheelectronsmakingupthebond
FormalCharge=valencee-–(unbondede-+½bondinge-)
OxidationNumber
Bondingelectronsaretransferredcompletelytothemoreelectronegativeatom
Half-Reactions
Redoxreactionscanbewrittenintermsoftwohalf-reactions
Oneinvolvesthelossofelectrons(oxidation)
Theotherinvolvesthegainofelectrons(reduction)
Example:Fe2++Ce4+→Fe3++Ce3+
Abalancedredoxequationhastohavechargebalance
Numberofelectronslostintheoxidationhalf-reactionmustbeequaltothenumberofelectronsgainedinthereductionhalf-reaction
RulesforBalancingRedoxReactionsBalancingRedoxEquationswithIon-ElectronMethodorHalf-ReactionMethod
Writetwohalf-reactionsandbalancebothfor:
Thenumberofthekeyatom(i.e.theatomchangingoxidationnumbers)
Changeinoxidationnumberwithelectrons
Addhalf-reactionssoelectronscancel
BalancechargewithOH-(ifthereactionisoccurringinabase)orH+
(ifthereactionisoccurringinanacid)
BalanceOatomswithH2O
Checkthatthereisnonetchangeinchargeornumberofatoms
OxidationNumberMethod
Determineoxidationnumberofatomstoseewhichonesarechanging
Putincoefficientssothatnonetchangeinoxidationnumberoccurs
Balancetheremainingatomsthatarenotinvolvedinchangeofoxidationnumber
Example:Considerthereaction:HNO3+H2S→NO+S+H2O
Oxidationnumbers:N=5,S=-2→N=2,S=0
Ngoesfrom5→2
Δ=−3reduction
Sgoesfrom-2→0
Δ=+2oxidation
MultiplyNby2andSby3
2HNO3+3H2S→2NO+3S+H2O
BalanceOinH2O
6(Ox)→2(Ox)+4H2O
Writethefinalreactionandmakesureitisbalanced(samenumberofatomsonleftandrightside)
2HNO3+3H2S→2NO+3S+4H2O
Voltaic(Galvanic)Cells
Voltaiccellsareelectrochemicalcellsinwhichaproduct-favored(spontaneous)redoxreactiongeneratesanelectriccurrent.Thereactionproducesanelectronflowthroughanoutsideconductor(wire).Requirementsforvoltaiccells:
Anode-anelectrode(i.e.conductorsuchasmetalstriporgraphite)whereoxidationoccurs
Cathode-anelectrodewherereductionoccurs
Saltbridge-tubeofanelectrolyte(sometimesinagel)thatisconnectedtothetwohalf-cellsofavoltaiccell
Saltbridgeallowstheflowofionsbutpreventsthemixingofthedifferentsolutionsthatwouldallowdirectreactionofthecellreactants
Chargedoesnotbuildupinhalfcells
Electricalneutralitymustbemaintained
CellDiagrams
Celldiagramsareshorthandrepresentationforanelectrochemicalcell.
Anodeisplacedontheleftside
Cathodeisplacedontherightside
Singleverticallinerepresentsaboundarybetweenphases,suchasbetweenanelectrodeandasolution
Adoubleverticallinerepresentsasaltbridgeorporousbarrierseparatingtwohalf-cells
ElectronPotential
Electronflowingalvaniccellcandowork/produceenergy
Electricalpotentialenergyismeasuredinvolts
1volt=(1joule)/(1coulomb)
Coulombs=amperesxseconds:
C=AxsorA=C/s
StandardCellVoltages
Cellvoltagescanbemeasuredunderstandardconditions:1atmpressure,250C,and1.0Mconcentrations
DenotedasE0cell
Thestandardcellpotentialisthesumofthestandardpotentialsfortheoxidativehalf-reactionandthereductivehalf-reaction
IfE0cellispositive,thenetcellreactionissaidtobeproduct-favored
(spontaneous)
IfE0cellisnegative,thenetcellreactionissaidtobereactant-favored
(nonspontaneous)
StandardElectrodePotentials
Standardelectrodepotentialsaremeasuredforhalf-reactions,relativetoastandardhydrogenelectrodepotential(whichhasanassignedvalueof0volts).
Eachhalfreactioniswrittenasareduction
Eachhalfreactioncouldoccurineitherdirection
Themorepositivethestandardelectrodepotential,thegreaterthetendencytoundergoreduction
Thatmeansitisagoodoxidizingagent
Themorenegativethestandardelectrodepotential,thegreaterthetendencytoundergooxidation
Thatmeansitisagoodreducingagent
Ifahalf-reactioniswritteninthereversedirection,youmustflipthesignofthecorrespondingstandardelectrodepotential
Ifahalf-reactionismultipliedbyafactor,thestandardelectrodepotentialisnotmultipliedbythatfactor
CellPotentialandGibbsFreeEnergy
SinceapositiveE0cellindicatesaspontaneousreaction,youmight
imaginethereisrelationshipbetweenE0cellandfreeenergy(ΔG0)
ΔG0=-nFE0cell
n=#ofmolesofelectronstransferred
F=Faradayconstant=9.65x104
Important:ApositiveE0cellwouldresultinanegativeΔG0,
andanegativeE0cellwouldresultinapositiveΔG0
ElectrolyticCells
Electrolyticcellsconsistofanelectrolyte,itscontainer,andtwoelectrodes,inwhichtheelectrochemicalreactionbetweentheelectrodesandtheelectrolyteproducesanelectriccurrent.
Propertiesofelectrolyticcell
Requiresenergy(intheformofanelectriccurrent)
Nophysicalseparationisneededforthetwoelectrodereactions
Usuallynosaltbridgeisrequired
Conductingmediumismoltensaltoraqueoussolution
Forelectrolyticredoxreaction:
E0cellisnegative
ΔG0ispositive
Kcissmall(<1)
CHAPTER18-NUCLEARCHEMISTRY
RadioactivityRadioactivityistheemissionofionizingradiationorparticlescausedbythespontaneousdisintegrationofatomicnuclei.
Typesofradioactivity:alpha,beta,andgammadecay
AlsopositronemissionConventiontobeawareof:
NuclearEquationSumoftheatomicnumbersonbothsidesofthenuclearequationmustbeequalSumofthemassnumbersonbothsidesofanuclearequationmustbeequal
NuclearEquationExample:
AlphaDecay
Alphaparticlesarenucleardecayparticles
Anunstablenucleusemitsasmallpieceofitself
Alphaparticlesconsistoftwoprotonsandtwoneutrons
Alphaparticlesymbol:α
An particleisaheliumnucleus
AlphaParticle:
Alphaparticlesareejectedfromthenucleusatafairlylowspeed(approximatelyone-tenththespeedoflight)
Theyareaminimalhealthrisktopeopleunlessingestedorinhaled
Largemassnucleitendtousealphaemissionbecauseitisaquickwayforalargemassatomtolosealotofnucleons(eitheraprotonorneutron)
AlphaDecayEquationExample:
BetaDecay
Betaradiationsymbol:βor
Betaemissionisanucleardecayprocessthatejectsahighspeedelectronfromanunstablenucleus
Electronisformedwithinthenucleusbythebreakdownofaneutronintoaprotonandelectron
Theelectronisejectedfromthesystem
Theprotonthatwasformedremainsbehindinthenucleus
Becauseoftheadditionoftheproton,theatomicnumberofanelementincreasesduringbetaemission
Betaemissioncanbeasignificanthealthrisk
BetaDecayEquationExample:
GammaDecay
Gammaradiationsymbol:
Gammaemissionoccursprimarilyaftertheemissionofadecayparticle
Gammaisaformofhighenergyelectromagneticradiation
Itisasignificanthealthrisk
Afteraparticleisejectedfromanucleusthesystemmayhavesomeslightexcessofenergy,orexistinameta-stablestate
Thisslightexcessofenergyisreleasedasgamma
Gammaemissiondoesnotresultinchangeoftheisotopeortheelement
Nomassandnochargechange
GammaDecayEquationExample:
Theasteriskisusedtorepresentthattheelementisinahighenergystate
PositronEmissionAnunstablenucleusemitsapositronApositronhasthesamemassasanelectronbutthechargeis+1
PositronEmissionEquationExample:
Half-life
Half-lifeisdefinedasthetimefor½oftheparentnuclidestodecaytodaughternuclides.
Allradioactivedecayisfirstorder
Rate=
t–time
N-#ofatoms
k=rateconstant
ln(No/N)=k
No-#ofatomsatthestartingtime
Half-lifeformula:
Half-lifeisaconstant
Carbon-14Dating
Carbon-14datingcanbeusedtodateobjectsrangingfromafewhundredyearsoldto50,000yearsold
Carbon-14isproducedintheatmospherewhenneutronsfromcosmicradiationreactwithnitrogenatoms
147N+10n→146C+11H
Livingthingstakeincarbondioxideandhavethesame 14Cto12Cratioastheatmosphere
However,whenaplantoranimaldies,itstopstakingincarbonasfoodorair
Radioactivedecayofcarbonstartstochangetheratioof 14C/12C
Bymeasuringhowmuchtheratioislowered,wecandeterminehowmuchtimehaspassedsincetheplantoranimallived
Half-lifeofcabon-14is5,720years
FissionandFusionInfission,alargemassnucleusissplitintotwoormoresmallermassnuclei
FissionEquationExample:
Infusion,smallmassnucleiarecombinedtoformalargermassnucleus
FusionEquationExample:
Fusionrequiresveryhightemperatures(inthemillionsofdegrees)sothatsmallnucleicancollidetogetheratveryhighenergies
CONCLUDINGREMARKS
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