# How to prove empirical and molecular formulae?

Aug 8, 2017

$\text{How to prove.........?}$

#### Explanation:

You can seldom prove anything unequivocally in science. You can find data that are consistent with a theoretical framework.

And the yard stick of consistency is evidence gathered from some (or several) experiments.

To find the empirical formulae of alkanes............alkynes etc., take a known mass of hydrocarbon, combust it in a furnace, and collect the combustion gases of carbon dioxide, and water. The quantities of water and carbon dioxide may be very precisely measured (by gas chromatography). They are usually reported as %C and %H by mass in the sample, and we can use these percentages to find the empirical formula (and you must have done examples of these problems). %N can also be measured directly as nitrogen comes off as $N {O}_{2} \left(g\right)$.

If the material contains oxygen, then the missing percentage is assumed to be due to %O. Halide percentage may be measured by a Mohr titration.