CHEM101P
Prepara0onforGeneralChemistry
Chapter3a
The Mole
Collec0onsofItems
•  WhataboutforChemistry?Themassofasingleatomistoo
smalltomeasureonabalance!
massofhydrogenatom=1.673×10-24g
TheMole
•  Soweneedareallybigunittoexpresslargenumbers:
1mol=NA=6.0221367x1023
Avogadro’snumber(NA)
•  Thisnumber(6.022×1023)iscalledAvogadro’s Number
(NA).
•  Thisisthesamenumberofpar0clesasthereareinexactly
in12.00000……gramsofcarbon-12(12C).
TheMole
AmedeoAvogadro
TheMole
•  Amoleofamarbles hasAvogadro’snumberofmarbles:
willcoverthesurfaceoftheUSAbya50-mile-thicklayer!
TheMole
•  Themoleistheconnec0onbetweenthemicroscopicand
themacroscopic:
TheMole
•  Themoleistheconnec0onbetweenthemicroscopicand
themacroscopic:
12.00gx1amux1C-12atom=
1mol1.6605x10-24g12amu
6.022x1023C-12atoms
mol
TheMole
•  Amoleofaelement hasAvogadro’snumberofatoms:
1molNa=6.022x1023Naatoms
•  Amoleofacovalent compound hasAvogadro’snumberof
molecules:
1molCO2=6.022x1023CO2molecules
•  Amoleofaionic compound hasAvogadro’snumberof
formulaunits:
1molK2SO4=6.022x1023K2SO4formulaunits
TheMole
•  Onemoleof:
Avogadro’sNumber
•  canbewri\enasanequalityandtwoconversionfactors.
Equality:
1mol=6.022x1023par0cles
ConversionFactors:
6.022x1023par0clesand1mol
1mol 6.022x1023par0cles
Avogadro’sNumber
•  Howmanyatomsaretherein42.67molofcopper?
Avogadro’sNumber
•  Howmanymolesofsilveris8.46×1024atomsofsilver?
TheMassofaMole
•  Wesaidthatamolecontainsthesamenumberofpar0cles
asthereareinexactlyin12.00000…gramsofcarbon-12
(12C).
•  So1moleofC-12weighsexactly12g.Thisisthemolar
massofC-12.
•  Wealreadyknewthat1atomofC-12weighsexactly12
amu,i.eitsatomic mass.
Foranyelement
atomicmass(amu)=molarmass(grams)
TheMassofaMole
Foranyelement
atomicmass(amu)=molarmass(grams)
TheMassofaMole
•  Bothboxescontainsadozennails,butthesecondboxis
lighterinmass.
TheMassofaMole
•  Amoleofsucroseweighsmorethanamoleofwater.
MolecularMass
Themolecular mass is:
•  Themassofonemoleculeofacovalentcompound(inamu).
•  Thesumofthemassesoftheatomsinasinglemolecule.
1S
32.066amu
2O +2x15.9994amu
SO2
64.0648amu
SO2
=64.065amu
Foranymolecule
molecularmass(amu)=molarmass(grams)
1moleculeSO2=64.065amu
1moleSO2=64.065gSO2
MolarMass&MolecularMass
FormulaMass
Theformula mass is:
•  Themassofoneformulaunitofanioniccompound(inamu).
•  Thesumofthemassesoftheatomsinasingleformula
unit.
1Na
22.9898amu
1Cl
+35.453amu
NaCl
NaCl
58.4428amu
=58.443amu
Foranyioniccompound
formulamass(amu)=molarmass(grams)
1formulaunitNaCl=58.443amu
1moleNaCl=58.443gNaCl
FormulaMass
•  CalculatetheformulamassofAl2(SO4)3.
MolecularMass
•  CalculatethemolecularmassofTylenol.
Tylenol
MolarMass
•  canbewri\enasanequalityandtwoconversionfactors.
Equality:
1mol=12.00000gforCarbon
ConversionFactors:
12.00000gCand1molC_ 1molC 12.00000gC
MolarMass
•  Howmanymolesaretherein225gofoxygengas?
•  What is the mass in grams of 4.82 moles of silver
phosphate?
Roadmaps
atoms
molecules
mL
density
atoms
molecules
Roadmaps
•  Howmanyformulaunitsarein50.0goflead(IV)oxide?
Roadmaps
•  Calculatethemassof7.64x1022Satoms.
ChemicalFormulasasConversionFactors
•  Ifthereare3spidersinaroom,howmanyspiderslegsare
there?
ChemicalFormulasasConversionFactors
•  Ifthereare3watermoleculesina0ny-0ny-0nydrop,how
manyHatomsarethere?
ChemicalFormulasasConversionFactors
Moles of compound
1 mol NaCl
1 mol H2O
1 mol CaCO3
1 mol C6H12O6
Moles of constituents
1 mol Na, 1 mol Cl
2 mol H, 1 mol O
1 mol Ca, 1 mol C, 3 mol O
6 mol C, 12 mol H, 6 mol O
Moles of compound
1 mol NaCl
1 mol CaCO3
1 mol Na2CO3
Moles of constituents
1 mol Na+, 1 mol Cl1 mol Ca2+, 1 mol CO322 mol Na+, 1 mol CO32-
ChemicalFormulasasConversionFactors
•  Calculatethemolesofoxygenin1.7molesofCaCO3.
Roadmaps
•  How many N atoms are in 56.04 g of dinitrogen
tetrahydride?
Roadmaps
•  Calculatethenumberofchlorideionsin1.38gof
magnesiumchloride?