What is the difference between molecular mass and formula unit mass?

1 Answer
Aug 14, 2017

The same as the difference between molecules and ionic compounds...

  • Molecular mass is used for molecules, i.e. covalently-bonded multi-atomic substances.


  • Formula unit masses are used to describe ionic compounds, i.e. ionically-bonded compounds found as lattice structures. One formula unit of sodium chloride, #"NaCl"#, is found in...


It makes no physical sense to prescribe a molecular mass to #"NaCl"#, nor does it make physical sense to designate #"CO"_2# as a formula unit.