A molecule with molecular weight of 180.18 g/mol is analyzed and found to contain 40.00% carbon, 6.72% hydrogen and 53.28% oxygen. What are the empirical and molecular formulas of the molecule?
The empirical formula is CH₂O and the molecular formula is C₆H₁₂O₆.
Assume we have 100 g of the compound.
Then we have 40.00 g of C, 6.72 g of H, and 53.28 g of O.
Moles of C = 40.00 g C ×
Moles of H = 6.72 g H ×
Moles of O = 53.28 g O ×
Moles of C:Moles of H:Moles of O = 3.331:6.67:3.330=1.000:2.00:1 ≈ 1:2:1
The empirical formula is CH₂O.
The empirical formula is the simplest formula of a compound. The actual formula is an integral multiple of the empirical formula.
If the empirical formula is CH₂O, the actual formula is
The empirical formula mass of CH₂O is 30.03 u. The molecular mass of 180.18 u must be some multiple of this number.
∴ The molecular formula =
Hope this helps.