What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen?

The empirical formula is C₃H₃O.

Moles of C = 65.5/12.01
= 5.45 mol C
Moles of H = 5.5/1
= 5.5 mol H
Moles of O = 29.0/16
= 1.81 mol H
Moles of C: Moles of H: Moles of O =5.45: 5.5: 1.81 =
3.01: 3.0: 1 ≈ 3:3: 1
The empirical formula is C₃H₃O.