How To: Find molar mass

Find molar mass

It's time for science. You are able to calculate the molar mass for a compound using the periodic table and the amount of compound involved. You might need to know this in your everyday life but you will definitely need this in a chemistry class.

The molar mass of a chemical compound is the mass, in grams, of 1 mole of the substance.

You Will Need

* A periodic table
* A chemical compound formula
* Molar masses of elements

Step 1: Find molar mass of an element

Find the molar mass of an element. In grams, molar mass is numerically equal to the element's atomic weight in atomic mass units, which you can find on the periodic table of the elements.

Step 2: Calculate diatomic elements

Remember that seven elements – hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine, are diatomic elements. As pure elements, they form molecules containing two atoms. To find the molar mass of a diatomic element, multiply its atomic weight by two.

Step 3: Consider chemical compounds without subscripts

If you're working with a chemical compound – a combination of elements – whose formula does not contain any subscripts, add the molar masses of each of the elements.

Step 4: Consider chemical compounds with subscripts

If your compound does contain subscripts, multiply the number of atoms of any element or chemical group with a subscript by the subscript value.

For example, the molar mass of iron chloride is (1 atom times 56 grams/mole iron) plus (2 atoms times 35.5 grams/mole chlorine) equals 127 grams/mole iron chloride.

Step 5: Consider chemical compounds with more complicated formulas

If you're working with a compound that has more complicated subscripts, take into account the total number of atoms present in the compound.

Step 6: Use the calculation

Use molar mass in all kinds of chemistry calculations, including finding the molecular formula of a substance.

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