Question

How do you determine empirical and molecular formulas of a compound?

Answer 1

See this old answer and links.

Explanation:

Well the percentage composition of an organic comound is determined by taking an accurate mass of the sample and combusting it in a furnace to give `CO_2` and water. This gives you percentage composition with respect to carbon and hydrogen.

Now an empirical formula can be assessed from these results. However, to determine the molecular formula, you need some way of determining the molecular mass of the compound. The molecular formula will always be a multiple of the empirical formula:

i.e. `("Empirical formula")xxn="Molecular formula"`.

See here for some more spray.