# What is an empirical formula?

Jan 26, 2017

It's a ratio formula of all the elements in the compound.

#### Explanation:

A ratio formula doesn't say anything about the actual numbers of atoms and how they are interconnected.

Example:
By burning a carbon-hydrogen compound and measuring the water and $C {O}_{2}$ we get the empirical formula $C {H}_{2}$.

This means the compound has a molecular formula of ${C}_{n} {H}_{2 n}$, or amounts of $C$ and $H$ atoms in the ratio 1:2.
So it could be ${C}_{2} {H}_{4}$ (ethene), ${C}_{3} {H}_{6}$ (propene), any other "-ene", or a lot of others (like cyclo-hexane).

Determining the molecular mass (step two) may lead to a molecular formula, which tells us the right number of atoms in the molecule, but still nothing about how they are connected.

Jan 26, 2017

For example the Empirical formula of Butane (${C}_{4} {H}_{10}$) is ${C}_{2} {H}_{5}$.