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MOLAR MASS
WHAT IS MOLAR
MASS?
 Molar mass is the weight of one mole
(or 6.02 x 1023 molecules) of any
chemical compounds. Molar masses of
common chemical compounds that
you might find in the chemistry
laboratory can range between 18
grams/mole for compounds like
water to hundreds of grams per mole
for more complex chemical
compounds.
CALCULATE THE MOLAR MASS OF
AN ELEMENT:
 The molar mass of elements is found by
looking at the atomic mass of the element on
the periodic table. For example, if you want
to find the molar mass of carbon, you would
find the atomic mass of carbon on the
periodic table, and this is equal to the molar
mass in grams per mole. So, in our example,
carbon has a molar mass of 12.01 grams per
mole.
 Exeptions: H2, N2, O2, F2, CL2, BR2, I2.
 Meaning the element have two atoms and we
need to multiply by two each o their atomic
mass.
CALCULATE THE MOLAR MASS OF
A CHEMICAL COMPOUND:
 1. Molar masses of chemical compounds
are equal to the sums of the molar
masses of all the atoms in one molecule
of that compound. If we have a chemical
compound like NaCl, the molar mass will
be equal to the molar mass of one atom
of sodium plus the molar mass of one
atom of chlorine. If we write this as a
calculation, it looks like this:
 (1 atom x 23 grams/mole Na) + (1 atom
x 35.5 grams/mole Cl) = 58.5
grams/mole NaCl
 2. If you have a subscript in a chemical
formula, then you multiply the number of
atoms of anything next to that subscript by
the number of the subscript. For most
compounds, this is easy. For example, in iron
(II) chloride, or FeCl2, you have one atom of
iron and two atoms of chlorine. The molar
mass will be equal to (1 atom x 56
grams/mole Fe) + (2 atoms x 35.5
grams/mole of chlorine) = 127 grams/mole
of iron (II) chloride.
EXAMPLES
Sodium Fluoride

In sodium fluoride, there is one atom
of sodium and one atom of fluorine.
The molar mass will then be:
(1 atom x 23 grams/mole of sodium)
+ (1 atom x 19 grams/mole of
fluorine) = 42 grams/mole of sodium
fluoride
Copper (l) Chloride
 In copper (I) chloride, there is one
atom of copper and one atom of
chlorine. The molar mass is then (1 x
63.5 grams) + (1 x 35.5 grams) = 99
grams/mole of copper (I) chloride
Calcium Fosfate

In calcium sulfate, there is one atom
of calcium, one atom of sulfur, and
four atoms of oxygen. The molar mass
is then (1 x 40 grams) + (1 x 32
grams) + (4 x 16 grams) = 136
grams/mole of calcium sulfate
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