Question

How do we determine the molecular formula of a carbonyl species, `C_nH_(2n)O`?

Answer 1

Without a molecular weight determination you are a shot bird..........

Explanation:

Formaldehyde, acetaldehyde, acetone, all the MONOFUNCTIONAL ketones and aldehydes have a formula of `C_nH_(2n)O`. For formaldehyde, `n=1`, but `n` could equal `2,3,4.........`, and generate the same empirical formula.....

TO get the molecular formula, you need a molecular weight determination. Got one?

A useful idea to develop in this context is the so-called degree of unsaturation. You have the one degree of unsaturation for this problem.