posted by Some kid. on .
The relative molecular mass of A is 116. Determine the molecular formula for A.
What's the empirical formula?
Calculate the empirical molar mass (by adding the atomic masses of the elements). Let's just suppose CxHyOz = 57. So divide 116/57 = 2.03. Round that to a whole number (the relative molar masses are usually done by a procedure that gives only approximate molar masses) which in this case is 2. That means the empirical formula is 1/2 the molecular formula; i.e., (CxHyOz)2 = molecular formula. Then you can add the atomic masses to obtain an exact molar mass.