Monday,October9th,2017

APChemistryDay15

CW/HWAssignments2.  Ch.3NotesPartA10/9

3.  Ch.3Packet10/9

PLANNER •  Ch.3Packet•  StudyCh.3+Ch.5•  TurninUnitLogs•  WriteunitstandardsforUnit3

EssenMalknowledgestandards•  1.A.1:MoleculesarecomposedofspecificcombinaMonsofatoms;differentmoleculesare

composedofcombinaMonsofdifferentelementsandofcombinaMonsofthesameelementsindifferingamountsandproporMons

•  1.A.2:ChemicalanalysisprovidesamethodfordeterminingtherelaMvenumberofatomsinasubstance,whichcanbeusedtoidenMfythesubstanceordetermineitspurity

•  1.A.3:ThemoleisthefundamentalunitforcounMngnumbersofparMclesonthemacroscopiclevelandallowsquanMtaMveconnecMonstobedrawnbetweenlaboratoryexperiments,whichoccuratthemacroscopiclevel,andchemicalprocesses,whichoccurattheatomiclevel

•  1.D.2:AnearlymodeloftheatomstatedthatallatomsofanelementareidenMcal.Massspectrometrydatademonstrateevidencethatcontradictsthisearlymodel.

•  1.E.1:Physicalandchemicalprocessescanbedepictedsymbolically;whenthisisdone,theillustraMonmustconserveallatomsofalltypes.

•  1.E.2:ConservaMonofatomsmakesitpossibletocomputethemassesofsubstancesinvolvedinphysicalandchemicalprocesses.ChemicalprocessesresultintheformaMonofnewsubstances,andtheamountofthesedependsonthenumberandthetypesandmassesofelementsinthereactants,aswellastheefficiencyofthetransformaMon.

•  3.A.1:Achemicalchangemayberepresentedbyamolecular,ionic,ornetionicequaMon.

•  3.A.2:QuanMtaMveinformaMoncanbederivedfromstoichiometriccalculaMonsthatuMlizethemoleraMosfromthebalancedchemicalequaMons.Theroleofstoichiometryinreal-worldapplicaMonsisimportanttonote,sothatitdoesnotseemtobesimplyanexercisedoneonlybychemists.

FLT•  Iwillbeableto:–  ConnectthenumberofparMcles,moles,mass,andvolumeofsubstancestooneanother,bothqualitaMvelyandquanMtaMvely

–  ExpressthelawofconservaMonofmassquanMtaMvelyandqualitaMvelyusingsymbolicrepresentaMonsandparMculatedrawings

–  ApplyconservaMonofatomstotherearrangementofatomsinvariousprocesses

–  TranslateanobservedchemicalchangeintoabalancedchemicalequaMonandjusMfythechoiceofequaMontypeintermsofuMlityforthegivencircumstances

–  UsestoichiometriccalculaMonstopredicttheresultsofperformingareacMoninthelaboratoryand/ortoanalyzedeviaMonsfromtheexpectedresults

–  RelatequanMMestoidenMfystoichiometricrelaMonshipsforareacMon,includingsituaMonsinvolvinglimiMngreactantsandreacMonsthathavenotgonetocompleMon

•  Bycomple1ngCh.3Notes

Ch.3:Stoichiometry

ChemicalQuanMMesReview

Recall: Units • Whatareourunitsfor…

– Mass?• Grams!

– Volume?• Liters!

– Amount?• Moles!

What is the mole?

We�re not talking about this kind of mole!

The Mole § Mole (mol) = amount = defined as

the # of carbon atoms in exactly 12 g of carbon-12.

Moles (is abbreviated: mol) § 1 mole = 6.022 x

1023 particles or atoms or molecules

§ Avogadro’s Number = 6.022 x 1023

Similar Words for an amount §  Just like a dozen is 12, or a pair is

two, a mole is an amount. §  One dozen eggs = 12 eggs §  One mole of eggs = 6.022 x 1023

eggs

Figure3.4-One-MoleSamplesofSeveralElements

Table3.1-Comparisonof1MoleSamplesofVariousElements

Moles (is abbreviated: mol) § Writing conversions: mol à

particles

Types of questions ■ Howmanyoxygenatomsinthefollowing?CaCO3Al2(SO4)3

3 atoms of oxygen

12 atoms of oxygen

Ex/ § How many molecules of CO2 are

in 4.56 moles of CO2?

Ex/ § How many moles of water is 5.87

x 1022 molecules?

SampleQuesMon•  WhichofthefollowingisthemostaccuratedescripMonofamole?a.  Massofcarboninameasuredsampleofcarbon

b.  Numberofatomsinanygivenmassofanelement

c.  Numberofsodiumionsin58.44gofsodiumchloride

d.  AtleasttwooftheseareaccuratedescripMonsofamole

SampleQuesMon•  Whichofthefollowingisclosesttotheaveragemassofoneatomofcopper?a.  63.55g

b.  52.00g

c.  58.93g

d.  65.38g

e.  1.055×10–22g

MolarMass

Atomic & Molar Mass § Molar mass = Mass of 1 mole (g/mol) § Allows us to convert from mol ßà g § Ex/ Molar mass of Carbon

Ex/ § What is the mass of 2.34 moles of

carbon?

MolarMassforFormulas

Calculating Formula Mass

Calculate the formula mass of magnesium carbonate, MgCO3.

24.3 g + 12 g + 3 x (16.00 g) = 84.3 g

Thus, 84.3 grams is the formula mass for MgCO3.

MolarMass•  Example

•  Calciumcarbonate(CaCO3),alsocalledcalcite,istheprincipalmineralfoundinlimestone,marble,chalk,pearls,andtheshellsofmarineanimalssuchasclamsa.  Calculatethemolarmassofcalciumcarbonate

b.  Acertainsampleofcalciumcarbonatecontains4.86moles

•  Whatisthemassingramsofthissample?

•  WhatisthemassoftheCO32–ionspresent?

MolarMass•  SoluMon(a)

•  Thus,themassof1moleofCaCO3(1moleofCa2+plus1moleofCO3

2-)is100.09g

•  Thisisthemolarmass

MolarMass•  SoluMon(b)•  Massof1moleofCaCO3is100.09g

– Samplecontainsnearly5moles,orcloseto500g

– Exactamountisdeterminedasfollows:

•  Tofindthemassofcarbonateions(CO32–)presentinthis

sample,realizethat4.86molesofCaCO3contains4.86molesofCa2+ionsand4.86molesofCO3

2–ions

MolarMass•  SoluMon(b)

MolarMass•  Exercise:•  Calculatethemolarmassofthefollowingsubstances:

MolarMass•  Exercise:•  Whatnumberofnitrogenatomsarepresentin1.00gofeachofthefollowingcompounds?

SampleQuesMon•  Whichofthefollowing100.0-gsamplescontainsthegreatestnumberofatoms?a.  Magnesium

b.  Zinc

c.  Silver

d.  Calcium

e.  Allsamplescontainthesamenumberofatoms

SampleQuesMon•  Forwhichofthefollowingcompoundsdoes1.0grepresent2.27×10–2mol?a.  H2O

b.  CO2

c.  NH3

d.  C2H6

SampleQuesMon•  Massof0.82molofadiatomicmoleculeis131.3g

–  IdenMfythemolecule

a.  F2

b.  Cl2

c.  Br2

d.  I2

SampleQuesMon•  Whichofthefollowing100.0-gsamplescontainsthegreatestnumberofoxygenatoms?a.  H2O

b.  N2O

c.  C3H6O2

d.  CO2

e.  Allofthesampleshavethesamenumberofoxygenatoms

Recall

MassSpectrometer•  Helpstoaccuratelycomparethemassesofatoms

MassSpectrometer

•  Helpsdetermineaccuratemassvaluesforindividualatoms

•  DeterminestheisotopiccomposiMonofnaturalelements

AverageAtomicMass

•  Knownasatomicweight(asperIUPAC’sdeclaraMon),whichisdimensionlessbycustom–  IUPAC-InternaMonalUnionofPureandAppliedChemistry

•  Sinceelementsoccurinnatureasmixturesofisotopes,atomicmassesareusuallyaveragevalues

SampleQuesMon

•  Ex/TheatomicnumberofIndiumis49anditsatomicmass114.8g– Naturallyoccurringindiumcontainsamixtureofindium-112andindium-115,respecMvely,inanatomicraMoofapproximately:

a.  6:94

b.  25:75

c.  50:50

d.  75:25

e.  94:6

SampleQuesMon•  Ex/Youhaveasampleofzinc(Zn)andasampleofaluminum(Al)– Eachsamplecontainsthesamenumberofatoms

– Whichofthefollowingstatementsconcerningthemassesofthesamplesistrue?a.  Massofthezincsampleismorethantwiceasgreatasthe

massofthealuminumsample

b.  Massofthezincsampleismorethanthemassofthealuminumsample,butitisnottwiceasgreat

c.  Massofthealuminumsampleismorethantwiceasgreatasthemassofthezincsample

d.  Massofthealuminumsampleismorethanthemassofthezincsample,butitisnottwiceasgreat

e.  Massesofthetwosamplesareequal

PercentComposiMon

PercentComposiMon•  WaystoDescribeaCompound’sComposiMon:

•  Intermsofthenumbersofthecompound’sconsMtuentatoms

•  Intermsofmasspercent(weightpercent)

PercentComposiMon•  Ex/CalculaMngMassPercent

•  Carvoneisasubstancethatoccursintwoformshavingdifferentarrangementsoftheatomsbutthesamemolecularformula(C10H14O)andmass– OnetypeofcarvonegivescarawayseedstheircharacterisMcsmell,andtheothertypeisresponsibleforthesmellofspearmintoil

•  Computethemasspercentofeachelementincarvone

PercentComposiMon•  Ex/CalculaMngMassPercent-SoluMon

•  Wherearewegoing?– Tofindthemasspercentofeachelementincarvone

– Whatdoweknow?•  MolecularformulaisC10H14O

– WhatinformaMondoweneedtofindthemasspercent?•  Massofeachelement(we’lluse1moleofcarvone)

•  Molarmassofcarvone

PercentComposiMon•  Ex/CalculaMngMassPercent-SoluMon

•  Howdowegetthere?– Determinethemassofeachelementin1moleofC10H14O

PercentComposiMon•  Ex/CalculaMngMassPercent-SoluMon

– WhatisthemolarmassofC10H14O?

– Whatisthemasspercentofeachelement?•  FindthefracMonofthetotalmasscontributedbyeachelementandconvertittoapercentage

PercentComposiMon•  Ex/CalculaMngMassPercent-SoluMon

•  Realitycheck–  Individualmasspercentvaluesshouldtotalto100%withinround-offerrors

•  Inthiscase,percentagesaddupto100%

PercentComposiMon•  TryThese:•  CalculatethepercentcomposiMonbymassofthefollowingcompoundsthatareimportantstarMngmaterialsforsyntheMcpolymers:a.  C3H4O2(acrylicacid,fromwhichacrylicplasMcsare

made)

b.  C4H6O2(methylacrylate,fromwhichPlexiglasismade)

SampleProblem•  Whichofthefollowing100.0-gsamplescontainsthehighestpercentoxygenbymass?a.  H2O

b.  N2O

c.  C3H6O2

d.  CO2

e.  Allofthesampleshavethesamepercentoxygenbymass

DeterminingtheFormulaofaCompound

DeterminingtheFormulaofaCompound

•  Weighthesampleofthecompoundby:– DecomposingthesampleintoitsconsMtuentelements

– ReacMngitwithoxygen•  ResulMngsubstancesarethencollectedandweighed– ThistypeofanalysisisdonebyacombusMondevice

– Resultsofsuchanalysesprovidethemassofeachtypeofelementinthecompound,whichcanbeusedtodeterminethemasspercentofeachelement

DeterminingtheFormulaofaCompound

•  CombusMonDevice

•  Usedtoanalyzesubstancesforhydrogenandcarbon

•  Helpsdeterminethemasspercentofeachelementinacompound

DeterminingtheFormulaofaCompound

•  EmpiricalFormula

•  Anymoleculethatcanberepresentedas(CH5N)nhastheempiricalformulaCH5N– n-Integer– Molecularformula:Exactformulaofthemoleculespresentinasubstance

• Molecularformula=(empiricalformula)n•  Requirestheknowledgeofthemolarmass

DeterminingtheFormulaofaCompound

EmpiricalFormula�HowtoSolve1.  Assumeyouhave100gofyoursubstance(since

masspercentagegivesthenumberofgramsofaparMcularelementper100gofcompound)

– Eachpercentwillthenrepresentthemassingramsofthatelement

2.  Determinethenumberofmolesofeachelementpresentin100gofcompoundusingtheatomicmassesoftheelementspresent

DeterminingtheFormulaofaCompound

EmpiricalFormula�HowtoSolve3.  Divideeachvalueofthenumberofmolesbythe

smallestofthevalues–  IfeachresulMngnumberisawholenumber(arerappropriaterounding),thesenumbersrepresentthesubscriptsoftheelementsintheempiricalformula

–  Ifthenumbersobtainedarenotwholenumbers,mulMplyeachnumberbyanintegersothattheresultsareallwholenumbers

DeterminingtheFormulaofaCompound

MolecularFormula:1.  Obtaintheempiricalformula

2.  Calculatethemassoftheempricalformula

3.  CalculatetheraMo:n=MolarMass/EmpiricalFormulaMass

•  Integerfromtheprevioussteprepresentsthenumberofempiricalformulaunitsinonemolecule

DeterminingtheFormulaofaCompound•  Example

•  Awhitepowderisanalyzedandfoundtocontain43.64%phosphorusand56.36%oxygenbymass– Compoundhasamolarmassof283.88g/mol

• Whatarethecompound’sempiricalandmolecularformulas?

DeterminingtheFormulaofaCompound•  Example–SoluMon

•  Assume100g•  MassofP=43.64g

•  MassofO=56.36g

DeterminingtheFormulaofaCompound•  Example-SoluMon

– Whatarethemolesofeachelementin100.00gofcompound?

– Whatistheempiricalformulaforthecompound?•  Dividingeachmolevaluebythesmalleronegives

DeterminingtheFormulaofaCompound•  Example-SoluMon

• Sincewehave1Pand2.5O,wemulMplyby2togetwholenumbers

• Thisgivesus2Pand5O• SoourempiricalformulaisP2O5

DeterminingtheFormulaofaCompound•  Whatisthemolecularformula?

– Whatisthemolecularformulaforthecompound?•  Comparetheempiricalformulamasstothemolarmass

•  Molecularformulais(P2O5)2,orP4O10

SampleProblem•  EmpiricalformulaofstyreneisCH;itsmolarmassis104.1g/mol– Whatisthemolecularformulaofstyrene?

a.  C2H4

b.  C8H8

c.  C10H10

d.  C6H6

SampleProblem:•  Acompoundcontains47.08%carbon,6.59%hydrogen,and46.33%chlorinebymass– Molarmassofthecompoundis153g/mol

• Whataretheempiricalandmolecularformulasofthecompound?

Mole�VolumeRelaMonship

Mole-Volume Relationship § Volume may be affected by

§ (1) Temperature § (2) Pressure

§ Consequently, we need to compare gases at a constant temperature and pressure for consistency

Mole-Volume Relationship § Standard

Temperature and Pressure (STP): § 1 atm of

pressure and 273 K (0°C)

Mole-Volume Relationship § Molar Volume:

§ At STP, 1 mole of any gas occupies a volume of 22.4 L

SampleProblems

Example § What is the volume of 4.59 mole of

CO2 gas at STP?

Recall § Density = mass/volume (g/L)

Example § The density of a gas is 1.964 g/L

at STP. What is the molar mass of the gas?

CHEMICALEQSREVIEW

Chemical Equations • Chemical Equation = Shorthand for a

chemical rxn using formulas and symbols

Chemical Equations

•  There are two parts to a reaction: 1.  Reactants = substances you start

with 2.  Products = substances you end up

with

Symbols • à = “yields” or “reacts to form”

Reactants à Products

Symbols •  + = “and”

Cu + Cl2 à CuCl2

Symbols • States of matter = indicated with

subscripts (s), (l), (g), or (aq)

2H2(g) + O2(g) à 2H2O(l)

Symbols •  aq = aqueous = dissolved in water

NaCl(aq) à Na+ + Cl-

Symbols • Double arrow = reversible rxn

Symbols • Others: Heat (Δ), energy, and

catalysts can be indicated on arrows

Symbols • A catalyst is a substance that is

added to speed up a reaction, but is not used or consumed by the reaction

WriMngEquaMons

Writing Equations • Ex 1/ Bromine and potassium iodide

react to form potassium bromide and iodine

***NOTE*** • Diatomic gases =

H, N, O, F, Cl, Br, I • Write as diatomic if

they are by themselves in a chemical equation

Writing Equations • Ex 2/ Iron and oxygen react to form

iron (III) oxide

Now, read these equations:

Fe(s)+O2(g)→Fe2O3(s)

Cu(s)+AgNO3(aq)→Ag(s)+Cu(NO3)2(aq)

NO2(g)N2(g)+O2(g)→

ConservaMonofMass

Law of Conservation of Mass •  Law of Conservation of Mass =

mass in a closed system can neither be created nor destroyed

Law of Conservation of Mass • What does this mean for us?

– In a balanced chemical equation, the number and kinds of atoms on each side of the equation should be equal.

Law of Conservation of Mass

Balancing Equations • A balanced equation has the same

number of each element on both sides of the equation

Balancing Equations • We use coefficients to indicate

multiples of molecules or compounds

Balancing Equations • Coefficients are multiples of the

entire formula • How does this affect each atom?

Coefficients • How many of each type of atom? 1.  3H2O 2.  2NO3 3.  3Ca(NO3)2

Rules 1.  Write out correct formulas (if not

already written) Ex/ Li + H3PO4 à H2 + Li3PO4

Rules 2. Count the # of atoms of each type on both sides

–  If possible, keep polyatomic ions together

Ex/ Li + H3PO4 à H2 + Li3PO4

Rules 3. Balance the elements one at a time by adding coefficients in front.

à Generally, balance H, O, & monatomic atoms last

Ex/ Li + H3PO4 à H2 + Li3PO4

Rules 4. Double-check ��always Ex/ Li + H3PO4 à H2 + Li3PO4

Rules Never’s: •  Never add or change subscripts on

formulas •  Never put a coefficient in the middle of a

formula

Try These: •  AgNO3+Cu→Cu(NO3)2+Ag

•  Mg+N2→Mg3N2

•  P+O2→P4O10

•  CH4+O2→CO2+H2O

• C3H8 + O2 à H2O + CO2

CW •  Ch.3Packet