To find the empirical formula of a hydrocarbon from combustion data, we determine the moles of carbon and hydrogen in the sample based on the CO₂ and H₂O produced. The steps are as follows:

Step 1: Calculate moles of carbon from CO₂
All carbon in the hydrocarbon is converted to CO₂. Given mass of CO₂ = 3.08 g.
Molar mass of CO₂ = 44 g/mol.
Moles of CO₂ = $\frac{3.08}{44}$ = 0.07 mol.
Since each mole of CO₂ contains 1 mole of C, moles of C = 0.07 mol.

Step 2: Calculate moles of hydrogen from H₂O
All hydrogen in the hydrocarbon is converted to H₂O. Given mass of H₂O = 0.72 g.
Molar mass of H₂O = 18 g/mol.
Moles of H₂O = $\frac{0.72}{18}$ = 0.04 mol.
Since each mole of H₂O contains 2 moles of H, moles of H = 2 × 0.04 = 0.08 mol.

Step 3: Find the simplest mole ratio (C : H)
Moles of C = 0.07, moles of H = 0.08.
Divide both by the smallest number (0.07):
C: $\frac{0.07}{0.07}$ = 1
H: $\frac{0.08}{0.07}$ ≈ 1.1429
To get whole numbers, multiply by 7: C becomes 7, H becomes 8.
Thus, the empirical formula is C₇H₈.

Final Answer: C₇H₈

Related Topics and Formulae

Combustion Analysis: A technique to determine the empirical formula of organic compounds by burning them and measuring the products CO₂ and H₂O.

Key Formulae:
- Moles of C = $\frac{\mathrm{mass\; of\; CO}2}{44}$
- Moles of H = 2 × $\frac{\mathrm{mass\; of\; H}2O}{18}$
- Empirical formula is found by simplifying the mole ratio of C to H to smallest whole numbers.