PreAP Chemistry
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 =____________________ H
2
O __________________________
How many atoms in 1.5 moles of copper? (9.0 x 10 23 atoms Cu)
How many moles in 5.6 x 10 20 molecules of CH
4
? (9.3 x 10 -4 mol CH
4
)
How many N atoms in 1.8 moles N
2
O
5
? (2.2 x 10 24 N atoms)
How many oxygen atoms in 3.5 moles of calcium nitrite? (8.4 x 10 24 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 H
2
O o Note: Mass of 1 molecule of water = _______________ ______
What is the molar mass of copper (II) nitrate? (187.55 g/mol Cu(NO
3
)
2
)
Practice Conversions
14 g Ag  mol Ag
102 g NaCl  mol NaCl
2.5 mol Ni  g Ni
4.8 mol H
2
O  g H
2
O
35 g Co  atoms Co
15 g CsCl  molecules CsCl
6.8 x 10 24 atoms Ne  L Ne
82 g BF
3
 F atoms
% Composition
%X = ( _______________________________ /
___________________________________
) x 100
MgCl
2
(25.5% Mg, 74.5% Cl)
Ca
3
(PO
4
)
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. C
2
H
6 o ______ carbons o ______ hydrogens
Empirical Formula shows the __________________ whole number ratio of __________________ in a compound molecular = C
2
H
6 empirical = _______________
What is the empirical formula?
C
6
H
2
O
6
BaCl
2
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 (PbCl
2
)

Find the empirical formula
175.0 g of MSG (C
5
H
10
O
5
NNa) 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 (Mn
2
O
3
)
72.4% Fe and 27.6% O (Fe
3
O
4
)

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 CH
(C
3
H
6
O
3
)
2
O and a molar mass of 90.0 g/mol.
A compound with a molar mass of 164.2 g/mol that is 73.14% C, 7.37% H, and
19.49% O. (C
10
H
12
O
2
)