For molecules and ionic compounds

The same procedure can be used for molecules and compounds. By adding together the relative atomic masses of the individual elements in a particular compound in their correct proportions, we get the relative molecular mass (RMM) of the compound this is equivalent to one mole of the compound and contains 6 X 10 formula units. 

If you are talking about a mole of any substance, then the particles or formula should be specified. If you are asked, what is the mass of one mole of hydrogen, would it be 1 g (hydrogen atoms) or 2 g (hydrogen molecules)  

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