Define formula mass

1.	Define formula mass
Answer» When a substance does not contain discrete molecules as their constituent units and have a three-dimensional structure, formula mass is used to calculate molecular mass which is sum of all the atomic masses of atom present in the formula.For example, in sodium chloride (NaCl) , sodium as chloride ions are arranged in a three-dimensional structure i.e. there are two different entities and not a single entity (like in a molecule). Therefore, the formula mass of NaCl = Mass of Na\xa0+Mass of Cl = (23 +35.5)u = 58.5 u.

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