Question

What is the difference between the `"molecular and empirical formulae?"`

Answer 1

The difference between an empirical formula mass and a molecular mass.........? See here and links.

Explanation:

The difference is a whole number multiple.

The molecular formula is always a whole number multiple of the empirical formula. Take a simple molecule such as `"ethane, " H_3C-CH_3`. The empirical formula is the simplest whole number multiple tha represents the atomic proportion of this formula, i.e. `CH_3`.

And given that `"molecular formula"` `=` `nxx"empirical formula"`, in this case `n=2`.

Typically, an analyst can give you a percentage composition of your compound; i.e. `%C, H, N`; this gives an empirical formula by standard means. And then this empirical formula is converted to a molcular formula if some way of assessing the molecular mass (i.e. mass spec., boiling point elevation) can be found.