Pre AP Chem
Intermolecular Forces Chapter 12 and Chemical Reactions Chapter 9
IntramolecularForcesorchemicalbonds(Chapter7)
Ionicbonds(cationdonateselectronsandanionacceptselectrons
Mg2++2Cl---àMgCl2MagnesiumChloride
Covalentbonds(nonmetal-nonmetalsharingofelectrons)
Ifelectronsharingiseventhenthemoleculeisnon-polar—alldivalentelements
Ifelectronsaresharedunevenlythenthemoleculeispolar---likeH2O
Metallicbonds(solidmetalslikeFe2+/Fe3+,Cu+/Cu2+etc…
IntermolecularForcestheforcesthatholdagroupofmoleculestogether(nottheIntramolecular
forcesorbonds).
Intermolecularforcesincreaseinthefollowingway:
LeastIMFgases<liquids<solidsgreatestIMF
Q.PutthephasesofH2OinorderofgreatestIMFtoleastandexplainwhy.
LondonDispersionForces—presentinallmoleculesbutparticularlyinnon-polarmolecules
(ex.diatomicelements).Electronscanbeshiftedsothatelectronsareshiftedinstaneouslyor
momentarilycausinganinstantaneousdipole.
Dipole(inamoleculeresultsfromthepartialpositivecharge(d+) andthepartialnegative
(d-)chargesothattheelectronsfromd+ aredrawntowardthed-.
Dipole-Dipoleistheattractionsofoppositechargesonpolarmolecules.
HydrogenBondingisaspecialtypeofdipole-dipoleattraction.Thepolarmoleculemusthave
H,N,OorFinordertoformH-bondswiththelonepairofelectronsontheelectronegativeelement.
Thed+ chargeontheHformsanIntermolecularbondwiththed- ontheelectronegativeelement.For
exampleH2O:becauseoftheH-bondstheboilingpointofwateris100oCwhichisquitehighfora
smallmoleculelikewater(molarmassof18g/mol).Sincemanywatersintheliquidstatecanbe
attractedtoeachothertheystayinaliquidformevenwhilebeingheated.Asthetemperaturesbegin
torisetheIMFbegintobreakatthatpointtheH2O(g)vaporizesandtheliquidwaterboils.
Q.WhichhasahighboilingptHForH2O,why?
Q.WhattypeofforcesareinvolvedinH2O,HF,CH4,CH3I,I2,MgCl2,NH3,H2S
Q.ExplainwhyisBPcorrelatedwithmolarmassbutitreallyisbecauseoftheelectrondensity.
Q.PutthefollowinginorderofhighesttolowestBP:NH3,NI3,PH3,NHCl2,PHCl2,
Whatreasoningdidyouusetodeterminetheorder?
ChemicalReactions:
A+B---------àC+D
Reactants-----------àProductsReactantsgotoform,yield,produceProducts
Symbolsinequations:+additionof2ormorereactantsyielding2ormoreproducts.
àseparatesthereactantsfromtheproducts-denotesareaction
denotesareversiblereaction
(s)solidstate
(ppt)asolidthatfallsoutofsolutioninthereaction
(l)aliquidstate
(aq)asubstanceinaaqueoussolution
(g)agasesstate
DH orDthereactionisheated
Wordequation:
Ex.Solidsodiumwasaddedtowaterwhichgaveoffheatandformedsodiumhydroxideand
hydrogengas.Writeouttheequation.
BalancingEquations:rememberthelawofconservationofmatter.
Thesamenumberofelementsonthereactantsideoftheequationmustequaltherightsideofthe
equation.
Ex.KOH(aq)+MgBr2(aq)àMg(OH)2(s)+KBr(aq)
Countalltheatomsonthereactantside-----Countalltheatomsontheproductside
1K
1Mg 1Mg 1K
1O
2Br 2O
1Br
1H
2H
Sowehave2Brand1Oonreactantside 1Brand2Oonproductside
Tobalancetheequationweneedtoadd2totheKOHand2totheKBr
2KOH(aq)+MgBr2(aq)àMg(OH)2(s)+2KBr(aq)
Always,increasethecoefficientsneverthesubscripts!!
TypesofReactions:
Synthesisreactions-isthechemicalreactionwhere2ormorereactantsproduceasingleproduct.
A+BàC
Ex:
H2(g)+Cl2(g)àHCl(l) SynthesisRXNs
K2O(s)+H20(l)àKOH(aq)
CaO(s)+H2O(l)àCa(OH)2(s)
2SO2(g)+O2(g)à2SO3(g)
CombustionReactions—willalwayscontainreactantO2(g)andCO2(g)product
A+O2(g)àCO2(g)
Ex:
C(s)+O2(g)àCO2(g) CombustionRXNs
CH4(g)+O2(g)àCO2(g)+2H20(l)
DecompositionReactions-thesinglecompoundbreaksdowninto2ormoreelementsornew
compounds
ABàA+B
Ex:
H20(g)àH2(g)+O2(g) DecompositionRXNs
H202(aq)àH2O(l)+O2(g)
H2CO3(aq)àH2O(l)+CO2(g)
2HgOà2Hg(l)+O2(g)
CaCO3(s)-DàCaO(s)+CO2(g)
NH4NO3(s)àN2O(g)+2H2O(g)
IonicEquation:
AqueousSolutions:thesoluteisdissolvedinthesolventwhichiswater.
(Whensaltsaredissolvedinwatertheyformions)
Ex.
NaCl(aq)àNa+(aq)+Cl-(aq)
IonicEquation
HCl(aq)àH+(aq)+Cl-(aq)
ReactionsinAqueousSolutionscanalsoformpptorsolids
Ex.
2NaOH(aq)+CuCl2(aq)à2NaCl(aq)+Cu(OH)2(s)
AgNO3(aq)+NaCl(aq)àNaNO3(aq)+AgCl(s)
IonicReactions:reactionsofionsinaqueoussolutions
Ex.
NaCl(aq)àNa+(aq)+Cl-(aq)
IonicEquation
HCl(aq)àH+(aq)+Cl-(aq)
NetIonicSolutions—hereyouareonlyconcernedwiththepartofthereactionthatismakingthe
solid/pptormakingagas.
Ex.
2NaOH(aq)+CuCl2(aq)à2NaCl(aq)+Cu(OH)2(s)ChemicalEqu.(DoubleReplace)
2Na+(aq)+2OH-(aq)+Cu2+(aq)+2Cl-(aq)à2Na+(aq)+2Cl-(aq)+Cu(OH)2(s)Ionicequation
2OH-(aq)+Cu2+(aq)àCu(OH)2(s)NetIonicequation
Ex.
2HI(aq)+Li2S(aq)àH2S(g)+2LiI(aq)ChemicalEquation(DoubleReplace)
2H+(aq)+2I-(aq)+2Li+(aq)+S2-(aq)àH2S(g)+2Li++2I-(aq)IonicEquation
2H+(aq)+S2-(aq)àH2S(g)NetIonicEquation
ReactivitySeriesofmetals:
Li>K>Ba>Ca>Na>Mg>Al>Mn>Zn>Cr>Fe>Cd>Co>Ni>Sn>Pb>H>Cu>Ag>Hg>Pt>Au
MostreactiveReactsw/H2OReactsw/acid
Reactsw/O2Leastreactive
ReactivitySeriesofhalogens:mostreactive/mostelectronegativeF>Cl>Br>Ileastelectroneg.
ReplacementReactions—Thisinvolvesreplacinganelementintherxn.
SingleReplacement:Arxnwheretheatomsofoneelementreplacetheatomsofanotherelementin
acompound.
A+BXàAX+B
Ex.
Mg(s)+Fe2O3(aq)àFe(s)+MgO(aq)SingleReplacementRXNs
2Li(s)+2H2O(l)à2LiOH(aq)+H2(g)
Zn(s)+2HCl(l)àH2(g)+ZnCl2(aq)
Fe(s)+2AgNO3àFe(NO3)2(aq)+Ag(s)
2Na(s)+2H2OàNaOH(aq)+H2(g)
Ni(s)+CuCl2(aq)àCu(s)+NiCl2(aq)
DoubleReplacementreaction:thereplacementofelementinacompound.Alldoublereplacement
rxnsproduceeitherH2O,a(ppt)or(g).Ionsdon’tchangetheirchargesinionexchangereactions.
Theanionandcationoftwocompoundstradeplaces.
AX+BYàAY+BX
Ex.
F2(g)+2NaBr(aq)à2NaF(aq)+Br2(l)DoubleReplacementRXNs
Br2(g)+2NaF(aq)àNoRxnThemorereactivehalogenFwillreplacethelessreactive
halogenBrbutnottheotherwayaround
Ex.
KI(aq)+Pb(NO3)2(aq)àKNO3(aq)+PbI2(s)DoubleReplacementRXN
Balanced---No!
1K 1Pb 1K
1Pb needwhat?
1I
2NO3 1NO3 2I
Balanced:--Yes!
2KI(aq)+Pb(NO3)2(aq)à2KNO3(aq)+PbI2(s)
Ex.KCN(ag)+HBr(aq)àKBr(aq)+HCN(aq)DoubleReplacementRXN
Ex.Wordequation—WhenHCliscombinedwithNaHCO3adoublereplacementreactiontakesplace
whataretheproducts?Canoneoftheproductsbedecomposed?
HCl(aq)+NaHCO3(aq)àH2CO3(aq)+NaCl(aq)DoubleReplacementRXN
H2CO3àH2O(l)+CO2(g)DecompositionReaction
Ex:Silvernitrateandsodiumchloridewereheatedtoyieldapptofsilverchlorideandsodiumnitrate.
WriteouttheChemicalEquation,IonicEquationandtheNetIonicEquationfortheDouble
replacementequation.