How to find molecular mass

The molecular mass or molecular weight is the total mass of a compound. It is equal to the sum of the individual atomic masses of each atom in the molecule. It is easy to find the molecular mass of a compound with these steps.

1. Determine the molecular formula of the molecule.
2. Use the periodic table to determine the atomic mass of each element in the molecule.
3. Multiply each element's atomic mass by the number of atoms of that element in the molecule.
4. This number is represented by the subscript next to the element symbol in the molecular formula.
5. Add these values together for each different atom in the molecule.
6. The total will be the molecular mass of the compound.

 For example, to find the molecular mass of NH₃, the first step is to look up the atomic masses of nitrogen (N) and hydrogen (H). H = 1.00794, N = 14.0067
Next, multiple the atomic mass of each atom by the number of atoms in the compound.
There is 1 nitrogen atom (no subscript is given for one atom).
There are 3 hydrogen atoms, as indicated by the subscript.

molecular mass = (1 x 14.0067) + (3 x 1.00794) molecular mass = 14.0067 + 3.02382 molecular mass = 17.0305