The molecular mass of benzene is 78 amu. Its percentage composition is 92.31 % C and 7.69 % H. Determine the molecular formula of benzene.

The molecular mass of benzene is 78 amu. Its percentage composition is

1.	The molecular mass of benzene is 78 amu. Its percentage composition is 92.31 % C and 7.69 % H. Determine the molecular formula of benzene.
Answer» SOLUTION :Step I. Empirical formula of benzene `{:("Element","Percentage","Atomic mass","Gram ATOMS (Moles)","Atomic ratio (Molar ratio)","Simplest WHOLE no. ratio"),("C",92.31,12,(93.31)/(12)=7.69,(7.69)/(7.69)=1,1),("H",7.69,1,(7.69)/(1)=7.69,(7.69)/(7.69)=1,1):}` Empirical formula of benzene = CH Step II. Molecular formula of benzene Empirical formula mass `= 12 +1 =13u` Molecular mass `= 78 u` `N=("Molecular mass")/("Empirical formula mass")=((78u))/((13u))=6` Molecular formula `= n xx` Empirical formula `=6xx CH = C_(6)H_(6)`.