Summary Chapter 3: Stoichiometry

3 1 Atomic Mass
atomicmass mass of atom in amu protons 6
averageatomicmassaverage of alltheisotopes

numerically6
neutrons12equal
2
1 themass of a carbon 12atom standard
atomicmass unit amu frac 12 amu


3 2 Avogadro's the MolarMass of an Element
mole mol amount of a substance to Avogadro's
Avogadro's number times
N
A
6
0
3
21 of oneatom amu

conversionsweight
Amedeo Avogadro
molar mass M mas right
left
K
g
s of 1 mole of a substance onemoleofatoms g



times
m
6
0
3
2
g
u
a1 one atom right
frac
left
m
N
A
g
div
m times
N
A
n

mass m of moles of element n number of atomsofelement N

times
m
n div
N
A

3 3 Molecular Mass
molecularmass sum of amus in

molecule3
4 The Mass Spectrometer
massspectrometer
turnsatomsof samplegasinto positiveions
magnetseparatesions by charge mass ratio em
Showshow manyisotopesare there their

masses3
5 Percent Composition of compounds
percent composition mass percentage of each element in
compoundn
x molar mass of element
times
01 of moles of element in
molar mass of compoundn 1 mole of the compound
changeto
to integerconvert
of
smallestmoles
gdivide by ratios
divideby each elementmoleof elementsempirical
formulamass
ofmoles

Msubscripts3
6 Experimental Determination of Empirical Formulas
identifying compounds experimentally
1 Chemanalysisshows grams of each element in compound
2 convert gs to moles for each element
3 find empirical formula

finding the molecularformula