Find the molecular formula of arene if, when burning 3.9 g of it, 13.2 g of carbon monoxide (4)

Find the molecular formula of arene if, when burning 3.9 g of it, 13.2 g of carbon monoxide (4) and 2.7 g of water were formed.

We find the amount of water: n (H2O) = 2.7 / 18 = 0.15 mol. We find the amount of carbon dioxide: n (CO2) = 13.2 / 44 = 0.3 mol. We look at the ratio of C and H – since the number of H atoms in H2O is 2, then n (H) = n (H2O) * 2 = 0.3; since one carbon dioxide molecule contains one carbon atom, then n (C) = n (CO2) = 0.3. The ratio of carbon atoms to hydrogen atoms in the desired arene is 1 to 1. The general formula for arenes is C (n) H (2n-6). We got that the number of carbon atoms is equal to the number of hydrogen atoms, which means n = 2n-6, which means n = 6.
Answer: C6H6.