Molar Mass is the mass
of one mole of a substance (6.02 x 10^{23 }
formula^{ }units). The unit for molar mass
(note it is the mass of a mole) is grams/mole.

Atomic Weight is the
molar mass of an element.

Formula Weight is the
molar mass of an IONIC
compound.

Molecular Weight
is the molar mass of a COVALENT
compound.

Molecular Mass is
the mass of a given molecule (NOT MOLES of molecules).
The units are atomic mass units (amu).

1amu =1.660 538 782×10^{–27} kg
1 amu is 1/12 the mass of a carbon-12 atom which has a
mass of 12.0000.

Reading
Simple Chemical Formulas-
Each element
begins with a CAPITAL letter. The _{subscript}
belongs to the element it follows and indicates how many
of that atom there are. If there is only 1 atom we do not
use subscripts.

H_{2}O
2 hydrogen 1 oxygen

Reading Compounds
that have (parenthesis's).

When there is
parenthesis's around a group of atoms we must multiply
each atom by the _{subscript }to get the total
number of each element.

Ca(NO_{3})_{2
}1
Calcium 2 Nitrogen and 6 Oxygen --> 3 x 2

How do we
determine molar
mass?

The molar mass is
calculated by taking the sum of the atomic weights of all
the atoms which form the molecule.

First
determine the number of each atom in the formula.

1. Water
is made up of 2 hydrogens and 1 oxygen.

Find the
molar mass.

2.
Multiply the number of each atom by its atomic weight
(found on the Periodic Table of the Elements).

H_{2}O

H
2 x 1.00794 =2.01588

Add them up
Molecular Weight=18.01528g/mol

For our class we can round to 1 decimal place
so 18.0g/mol