Question

What is the molecular formula of a compound with the empirical formula `CH` and a molar mass of 39.01 grams per mole?

Answer 1

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

Explanation:

And thus the molecular mass must be a whole number multiple of the empirical formula mass.

Here, clearly, `39.01*g*mol^-1` `=` `3xx(12.011+1.008)*g*mol^-1`

Thus the molecular formula `=` `C_3H_3`.

As far as I know, this result make no sense at all, inasmuch as there is no molecule with a formula of `C_3H_3`. (If I am not seeing something bleeding obvious, then someone will tell me!)

There is a cyclopropenyl cation, `C_3H_3^+`, but this would have a different molecular mass; why? Allene, `C_3H_4` does not fit this description.