Lecture'1:'Fraser' 'Chapter'313:'Formulas'and'Their'Meanings'
!
I.!Formulas!of!each!elements!in!its!lowest!energy!state!(38381)!
!
!A.!Most!elements!have!the!atom!as!their!lowest!energy!states!
!
!I.!Ex:!!
!
!
!B.!Seven!diatomic!elements:!!
!
!C.!Two!polyatomic!elements:!!
!
!D.!Allotropes:!!
!
!
!1.!Ex:!!
!
!
!2.!Ex:!!
!
!
1!
II.!Formulas!of!ions!
!
!A.!Memorize!ions!from!Nomenclature!handout!for!upcoming!quiz!
!
!B.!Trends!in!charges!of!monatomic!ions:!
!
!
!1.!Ex:!Cl8 !
!S28 !
!N38!
!
!
!
!2.!For!2+,!28!and!3+,!38,!list!number!first.!
!
III.!Formulas!of!ionic!solids:!no!discrete!molecules!
!
!A.!Formula!unit!(f.!u.):!!!
!
!
!1.!Ex:!!
!
!
2!
IV.!Empirical!Formula!(EF):!!
!
!A.!Ex:!Glucose!has!a!molecular!formula!(MF)!of!C6H12O6.!!
!!
!
!Its!EF!is!!
!
!B.!Ex:!Many!compounds!with!different!MFs!can!have!the!same!EF:!
!
!
Name'
MF'
EF'
!
18propene!
!
! 18butene!
!!
!
18pentene!
!
18hexene!
!
!
!!
!
3!
IV.!Molar!Mass:!mass!of!1!mol!of!parVcles!or!formula!units!(38382)!
!
!A.!Fraser!gives!definiVon!of!Molecular!Weight!and!Formula!Weight!–!don't!!
!
!worry!about!these.!
!!
!B.!Ex:!What!is!the!molar!mass!of!ethanol,!CH3CH2OH?!
!
!
!
!
!
!
!!
!C.!Ex:!How!many!H!atoms!are!in!32.3!g!ethanol?!
!
!
!!
!
4!
IV.!Percentage!composiVon!by!mass!
!
!A.!Ex:!What!is!the!mass!percent!carbon!in!benzoic!acid,!C6H5COOH?!
!
!!
!
5!
!
!B.!Empirical!Formula!(EF)!Problems!(38383)!
!
!
!
!
!
!1.!Ex:!In!a!student!lab!experiment,!it!was!found!that!0.5684!g!of!!
!magnesium!burns!in!air!to!form!0.9426!g!of!magnesium!oxide.!Find!the!!
!empirical!formula!of!this!compound.!(This!problem!is!taken!from!Problem!!
!Example!13:!Simplest!formula!from!combusVon!masses!in!the!online!text.!
!In!the!text!it!is!incorrect.!Here,!we!will!work!the!correct!answer).! !!
!
6!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!!
!
!
!
!
!
!2.!Ex:!A!mineral!contains!a!hydrate!of!nickel!(II)!sulfate!with!an!unknown!!
!number!of!waters!of!hydraVon,!NiSO4•xH2O!where!x!is!unknown.!If!a!!
!0.400!g!sample!of!mineral!is!heated!to!constant!weight!over!a!Bunsen!!
!burner,!its!mass!decreases!to!0.296!g.!What!is!the!value!of!x!for!this!!
!hydrate?!
7!
V.!CombusVon!Analysis:!process!that!burns!an!unknown!sample!containing!C,!H,!and!
O!in!oxygen!to!produce!CO2!and!H2O.!From!this!informaVon,!the!empirical!formula!
can!be!found.!Add!in!the!molar!mass,!and!the!molecular!formula!can!be!found.!
!
!
!
!
!
!
!
!
!
!
!
Chem1,!Stephen!Lower!
!
!
!
!
!A.!Definitely!visit!for!more!info!about!combusVon!analysis!calculaVons:!!
!hdp://preparatorychemistry.com/Bishop_CombusVon_Analysis.htm!
!
!!
8!
!A.!Ex:!Tartaric!acid!is!the!white!powdery!substance!that!coats!tart!candies!such!!
!as!Sour!Patch!Kids.!CombusVon!analysis!of!a!12.01!g!sample!of!tartaric!acid!–!!
!which!contains!only!C,!H,!and!O!–!produced!14.08!g!CO2!and!4.32!g!H2O.!What!is!!
!the!EF!of!tartaric!acid?!
!
!
!
!
!
!
!
!
!
!
!
!
!
!!
9!
B.!Ex:!!
!
!
!
!
!
!
!
!
!
!
!
!
!
!!
10!