For more than four decades, scientists have noticed a mysterious chemical in the treated drinking water of millions of people in the United States, but no one’s been able to pinpoint exactly what it ...

But they didn’t know this chemical’s molecular formula or structure. Now the mystery molecule has been identified as the ...

You can work out the molecular formula from the empirical formula, if you know the relative mass formula (M r) of the compound. Add up the atomic masses of the atoms in the empirical formula.