I would like to know how to convert ppm (parts per million) to moldm^-3?

Question

Also, is it dependent on the molecular weight of what you are converting or is it just dependent on the solvent?

Answer 1

ppm is mg/L, so you do need to know the molecular weight of the solute in order to do the conversion.

Answer 2

well, if ppm was indeed mg/l, it would be called mg/l.
ppm has no measuring unit, that´s why it is parts per million (of the same parts). mg/kg or microliter/l is more like it.