1. MOLAR MASS

2. WHAT IS MOLAR MASS?  Molar mass is the weight of one mole (or 6.02 x 10 23 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.

3. 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.

4. 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

5.  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 FeCl 2, 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.

6. EXAMPLES

7. 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

8. 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

9. 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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