# What is the empirical formula for C_6H_6?

It is simply $C H$.
If we were given a sample of benzene, we could perform combustion analysis and get an empirical formula of $C H$, after the benzene was combusted and the oxidation products of $C {O}_{2}$ and ${H}_{2} O$ were very accurately measured on a gas chromatograph. We would need a molecular mass determination before we could supply the molecular formula.