Molar (Formula) Mass
Where do we find the
atomic mass?
For every 1 mol,
there are 22.99g!
Molar Mass
Molar (Formula) Mass – mass of a
molecule
Units: g/mol
“grams per mol”
Example 1
Molecule = NaCl
Is the molecule ionic or covalent?
Ionic
(metal and nonmetal)
Name the molecule:
Sodium Chloride
No prefixes
for ionic
Example 1
# A atoms in
molecule x atomic
mass of A
Molecule = NaCl
N
a
1
x
22.99 g/mol
+
# B atoms in
molecule x atomic
mass of B
Add those numbers
Cl
1
x
35.45 g/mol
=
58.4 g/mol
Example 2
Molecule = Dihydrogen Monoxide
Is the molecule ionic or covalent?
Covalent
Write the formula:
H2O
(nonmetals)
Example 2
# A atoms in
molecule x atomic
mass of A
Molecule = H2O
H
2
x
1.01 g/mol
2.02 g/mol
# B atoms in
molecule x atomic
mass of B
Add those numbers
+
O
1
x
16.00
16.00 g/mol
g/mol
=
18.o2 g/mol
Example 3
Molecule = (NH4)2O
Is the molecule ionic or covalent?
Ionic
(has a polyatomic ion)
Name the molecule:
Made up of ions: NH4+ and O2Ammonium Oxide
Example 3
Molecule = (NH4)2O
N: 2 x 14 = 28
H: 8 x 1 = 8
O: 1 x 16 = 16
(NH4)2O: 52 g/mol
Example 4
Molecule = Beryllium Hydroxide
Is the molecule ionic or covalent?
Ionic
(has a polyatomic ion)
Write the formula:
Made up of ions: Be2+ and OHBe(OH)2
Example 4
Molecule: Be(OH)2
Be: 1 x 9.01 g/mol
O: 2 x 16 = 32 g/mol
H: 2 x 1.01 = 2.02 g/mol
Be(OH)2 = 43.03 g/mol
Group Practice
Check your answers when done
Chemical Formula Molar Mass
KF
Na3PO4
Al2(CO3)3
Ca(SCN)2
Iron (III) Oxide
Dicarbon Tetrafluroide
Lead (II) Chromate
Boron Sulfate
Practice by Yourself
In your notes, find the molar mass of:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
H2O2
NaNO3
H2S
(NH4)2S
Ca3(PO4)2
Mg(NO3)2
Lithium Nitride
Trinitrogen Pentabromide
Iron (III) Nitrate
Ammonium Carbonate