# How are empirical and molecular formulas related?

Jun 30, 2016

The molecular formula is always a whole number multiple of the empirical formula.

#### Explanation:

The empirical formula is by definition the simplest whole number ratio defining constituent atoms in a species. The molecular formula is always a whole number ratio of the empirical formula.

$\text{Molecular formula}$ $=$ $\text{(Empirical formula)} \times n$.

Of course, $n$ MIGHT equal $1$.

Typically an organic compound would be combusted where its combustion products, $C {O}_{2}$ and ${H}_{2} O$ could be measured very accurately against a standard; $N$ content (as ${N}_{2}$ or $N {O}_{2}$) could also be measured very accurately on a gas chromatograph.

These data allow an empirical formula to be calculated. Given a molecular mass (by some other means), the molecular formula may be adduced.

So the take home message:

$\text{Molecular formula}$ $=$ $\text{(Empirical formula)} \times n$.

And of course $n$, the multiplier, may be $1$.

Capisce?