The mass of polystyrene is easily estimated looking at its mass spectrum.
The spectrum has the shape of a comb with a large number of teeth.
Teeth are equally spaced.
In the region between 1000 and 3000, the spacing is 104.12 g/mol.
In the region between 3000 and 6000, the spacing is 104.18 g/mol.
If the
and the spacing is approximately 104.12 g/mol.
The spacing changes