The molecular formula is C₄H₈O.
We must calculate the masses of C, H, and O from the masses given.
Mass of C = 17.873 mg CO₂ × (12.01 mg C/44.01 mg CO₂) = 4.8774 mg C
Mass of H = 7.316 mg H₂O × (2.016 mg H/18.02 mg H₂O) = 0.818 48 mg H
Mass of O = Mass of compound - Mass of C - Mass of H
= (7.321 – 4.8774 – 0.818 48) mg = 1.6251 mg
Now, we must convert these masses to moles and find their ratios.
From here on, I like to summarize the calculations in a table.
Element m/mg n/mmol Ratio Integers
C 4.877 4 0.406 11 3.9984 4
H 0.818 48 0.811 99 7.9944 8
O 1.625 1 0.101 57 1 1
The empirical formula is C₄H₈O.
