Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Wednesday,September27th,2017
APChemistryDay12
Do-Now:TakeoutyourFRQpacketandturntoFRQ#4:1. Usetheanswerkeytoreviewyour
response2. Keepinmind:APFRQkeysare
guidelinestellinggraderswhattolookfor.Theyarenotgivingyoucompleteresponses.
3. GiveyourselfanapproximatescoreforeachsecHon,andgiveyourselfatotaloutof6points
Do-Now:– Now,wewillcompleteanFRQanalysis.– Usethekeyandyourresponsetocompletetheworksheet.
– Discusswithyourgroupifneeded– Evenifyouthinkyoureceivedfullpoints,thinkabouthowyoucouldrewriteyouranswertoexpressyourideasclearly,concisely,andinalogicalflow.
Announcements• UnitTest
– Bringcalculatorsandreferencesheets– FRQ/ResponsesecKononFriday– MCsecKononTuesday
• Labnextweek• Tradeindojopoints
CW/HWAssignments15. FRQMeta-Analysis9/2716. MassSpecNotes+Packet9/27
PLANNER • StudyfortestJJJ• Getallstamps• FinishFRQMeta-AnalysisandMassSpec.packet
FLT• Iwillbeableto:– UsedatafrommassspectrometrytoidenKfytheelementsandthemassesofindividualatomsofaspecificelement
– JusKfytheselecKonofaparKculartypeofspectroscopytomeasureproperKesassociatedwithvibraKonalorelectronicmoKonsofmolecules
• Bycomple1ngMassSpecNotes
MassSpectrometry
Recall
PhotoelectronSpectroscopy(PES)
• UsingPES,wecanidenKfyspecificelementsandalsocomparetheirionizaKonenergiesforspecificelectrons
IdealizedPESspectrumofphosphorus
IdealizedPESspectraofboronandfluorine
PhotoelectronSpectroscopy(PES)
Isotopes
Isotopes• AreallatomsofagivenelementidenKcal?• Whileatomsareneutralandhaveequivalentnumbersofprotonsandelectrons...
• Thenumberofneutronsmaydiffer• Becauseatomsmayhavevaryingnumbersofneutrons,theirmassmayalsodiffer
Isotopes• FrederickSoddy(1877-1956)proposedtheideaofisotopesin1912
• Isotopes=atomsofthesameelementhavingdifferentmasses,duetovaryingnumbersofneutrons.
• SoddywontheNobelPrizeinChemistryin1921forhisworkwithisotopesandradioacKvematerials.
Isotopes
• Elements occur in nature as mixtures of isotopes.
AverageAtomicMass
Atomic Mass§ Whatisthemassofanatomofoxygen?§ Itdepends,becausetherearedifferentkindsofoxygenatoms.
§ Wearemoreconcernedwiththeaverageatomicmass.
§ Averageatomicmass=weightedaverageoftheisotopesofagivenelementbasedontheabundance(%)innature
Atomic Mass• Each isotope has its own atomic
mass, thus we determine the average from percent abundance.
Calculating Atomic Mass• MulKplytheatomicmassofeachisotopebyitsabundance(expressedasadecimal),thenaddtheresults.
Example• Calculatetheaverageatomicmassofoxygen
Trythisoneinyourgroups:
SoluKon• a):
• Letx=abundanceofNe-20• 19.99x+21.00(1-x)=20.18• x=0.905• %abundaceNe-20=90.5%,Ne-22=9.5%
Average Atomic mass• ButhowdoscienKstsdeterminepercentabundanceandaverageatomicmass?
MassSpectrometry
MassSpectrometry• MassspectrometryprovidesmasstochargeraKoandprovidesuswithinformaKontodeterminethemolecularmassofatoms/moleculesinasample.
• High-energyelectronsbombardthesample,causingittoionize
• AnelectricfieldseparatestheionsbasedontheirmasstochargeraKoàthisdataiscompiledintoamassspectrum
• (itseparatesisotopesbymass)
MassSpectrometry
MassSpectrometry• LikePES,therelaKvesizeofthepeaksindicatestherelaKvenumberofparKcles
MassSpectrometry• Basedonthisspectrum,whatisthemostcommonisotopeofzirconiuminoursample?
• Zr-90hasthehighestintensity(tallestpeak),soitisthemostcommon
MassSpectrometry• GivenZr-90is89.905amu,Zr-91is90.906amu,Zr-92is91.905amu,Zr-94is93.906amu,andZr-96is95.908amu,calculatetheaverageatomicmassofzirconium.
• Seehowcloseyougetto91.22
BasedonthemassspectrumofatomY,whichofthefollowingstatementsisfalse?
a.peakAandpeakDcomefromatomsthathavethesamenumberofelectronsb.therearesevenisotopesofatomYc.peakCcomesfromthemostabundantisotopeofatomYd.peakDcomesfromanatomwith4moreprotonsthantheatomthatgavepeakB
Theiden1tyofcompoundYis:a. Zirconiumb. Molybdenumc. Americiumd. Einsteinium
Whichpeakcomesfromanatomwiththegreatestnumberofneutrons?a. Ab. Cc. Dd. Allpeakshavethesamenumberofneutrons
CW• MassSpecpacket
– ThispacketgoesbeyondthelevelofunderstandingrequiredontheAP
– FocusoninterpreKng/explaining/calculaKngmorethanunderstandinghowitworks
– AjemptallquesKons
• Studyforquiz