Amount of Substance: Formulas, Yield and Atom Economy

Empirical formula shows the simplest whole number ratio of atoms in a compound.
Molecular formula shows the actual number of atoms of each element in a compound.
Molecular formulas are multiples of the empirical formula.
Example: Ethane’s molecular formula is C2H4 and its empirical formula is CH2.
Yield and atom economy are metrics used to calculate the amount of useful product formed.
% yield is calculated as (mass of product formed / maximum theoretical mass of product) x 100.
% atom economy is calculated as (molecular mass of desired product / sum of molecular masses of all reactants) x 100.