PreAP Chemistry
Guided Notes: The Mole
What is a mole?
a ____________________ unit
comes from the ______________________word for ________________ or ____________________
abbreviated ________________________
1 mole = _______________________ pieces (__________________________ number)
Using Avogadro’s number
1 dozen eggs = ____________ eggs
1 mole eggs = ________________________ eggs
1 mole carbon = ____________________C _____________
1 mol water =____________________ H2O __________________________
How many atoms in 1.5 moles of copper? (9.0 x 1023 atoms Cu)
How many moles in 5.6 x 1020 molecules of CH4? (9.3 x 10-4 mol CH4)
How many N atoms in 1.8 moles N2O5? (2.2 x 1024 N atoms)
How many oxygen atoms in 3.5 moles of calcium nitrite? (8.4 x 1024 O atoms)
Molar Mass
the mass of 1 mole of a substance
atomic mass (on the periodic table) is measured in amu (atomic mass units)
1 C atom = 12.011 amu
1 mole of C atoms = 12.011 g
Molar mass of a compound
Add up the total mass for each element in the compound
E.g. Water H2O
o Note: Mass of 1 molecule of water = _______________ ______
What is the molar mass of copper (II) nitrate? (187.55 g/mol Cu(NO3)2)
Practice Conversions
14 g Ag  mol Ag
102 g NaCl  mol NaCl
2.5 mol Ni  g Ni
4.8 mol H2O  g H2O
35 g Co  atoms Co
15 g CsCl  molecules CsCl
6.8 x 1024 atoms Ne  L Ne
82 g BF3  F atoms
% Composition
%X = (_______________________________/___________________________________) x 100
MgCl2 (25.5% Mg, 74.5% Cl)
Ca3(PO4)2 (19.8% P, 41.3% O, 38.8% Ca)
Molecular formula
shows the actual __________________ and ____________________ of atoms found in one
__________________ of a _______________________
e.g. C2H6
o ______ carbons
o ______ hydrogens
Empirical Formula
shows the __________________ whole number ratio of __________________ in a compound
molecular = C2H6
empirical = _______________
What is the empirical formula?
C6H2O6
BaCl2
Empirical Formulas can be found from % composition
Assume ______________ of the substance (%  g)
Convert ____________ to _____________
Divide each ____________________ by the __________________ value to get _____________________
Watch for __________________ ___________________ – you must have ________________ number
subscripts
Find the empirical formula
63.53% Fe and 36.48% S (FeS)
74.51% Pb and 25.49% Cl (PbCl2)
Find the empirical formula
175.0 g of MSG (C5H10O5NNa)
o 56.15g C
o 9.43g H
o 74.81g O
o 13.11g N
o 21.49g Na
Find the empirical formula
69.6% Mn and 30.4% O (Mn2O3)
72.4% Fe and 27.6% O (Fe3O4)
Determining Molecular Formulas
Find the _________________ formula
Find the ___________________ ___________________ ___________________
___________________ ________________ molar mass (given) by ___________________ molar mass
to get _______
Multiply each ____________________ by ________
Find the molecular formula
A compound has an empirical formula of CH2O and a molar mass of 90.0 g/mol.
(C3H6O3)
A compound with a molar mass of 164.2 g/mol that is 73.14% C, 7.37% H, and
19.49% O. (C10H12O2)