Determine the molecular formula of the compound with an empirical formula of CH and a formula mass of 78.110 amu.
The empirical formula of the compound that we have to determine is CH. The molecular mass of the compound is given by 78.110 amu.
The atomic mass unit or amu is defined as 1/12 the mass of the carbon-12 atom and is equal to 1.660538782(83)*10^-27 kg. A hydrogen atom has an amu of 1.00794. The amu of CH is the sum of the amu of an atom of C-12 and an atom of hydrogen which gives 12 + 1.00794 = 13.00794.
The molecular mass of the compound we have to determine which is 78.110. Dividing this by 13.00794 gives us 6.0047. This can be taken as 6 as there are slight discrepancies introduced due the rounding up of numbers.
The molecular formula of the compound is therefore C6H6. This incidentally is the molecular formula of the compound benzene.