Question

How are empirical and molecular formulas related?

Answer 1

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.

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

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

Typically an organic compound would be combusted where its combustion products, `CO_2` and `H_2O` could be measured very accurately against a standard; `N` content (as `N_2` or `NO_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:

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

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

Capisce?