6.0221367E 23 atoms. Since magnesium has an atomic mass of 24, one mole of magnesium weighs 24 grams and contains 6.0221367E 23 atoms of magnesium. Of course, nobody would ever do that. Since atoms are too small to count, we must weigh out a mole of atoms. Molar mass is a unit that enables scientists to calculate the weight of any chemical substance, be it an element or a compound.
Molar mass is the sum of all of the atomic masses in a formula.
Once one determines the molar mass of a substance, it will be easy to measure out one mole of that substance. 1.00794 S 32.066 O 15.9994 Multiply each atomic mass by the number of atoms in the formula. In this example the results have been rounded off to the correct number of decimal places. To use this calculator, please enable Javascript on your browser or switch to a browser that supports Javascript. Formulas can have a max of two brackets open at the same time, and the molecule of crystallization must be placed last.