would be entirely consistent with the percent compositions given above: You cannot distinguish
between the two, or any multiple of the empirical formula, just by percent compositions alone.
Incidentally, this is how the term empirical formula gets its name: The word empirical means
experimental, and the values of percent compositions, obtained experimentally through simple
analytical techniques, only allow us to determine the empirical formula. (Of course, nowadays with
modern technology, we are not limited to experimental techniques that would only give us percent
compositions.)
For the second part of the question on the molecular formula, we can use the same approach
discussed earlier: Divide the molecular weight by the weight represented by the empirical formula.
The resultant value is the number of empirical formula units in the molecular formula. The
empirical formula weight of C 3 H 4 O 3 is:
3(12 g/mol) + 4(1 g/mol) + 3(16 g/mol) = 88 g/molThe molecular weight is given to be 264 g/mol. Therefore:
C 3 H 4 O 3 × 3 = C 9 H 12 O 9 is the molecular formula.