How are empirical and molecular formulas related?

1 Answer
Jun 30, 2016

Answer:

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?