Fuel with highest carbon mass fraction produces most CO2 per kg

Steps:

• Calculate molar mass (M) for each fuel using atomic masses (C=12, H=1, O=16).
• Compute carbon mass fraction: (number of C atoms × 12) / M.
• Determine CO2 mass per kg fuel: carbon fraction × (44/12).
• Compare: octane (3.09 kg CO2/kg), propane (3.00 kg), biodiesel (2.80 kg), ethanol (1.91 kg).

Why C is correct:

• Octane has the highest carbon mass fraction (96/114 ≈ 0.842), maximizing CO2 via C + O₂ → CO₂ stoichiometry.

Why the others are wrong:

• A: Biodiesel's oxygen lowers carbon fraction (216/282 ≈ 0.766).
• B: Ethanol's high oxygen and hydrogen content yields lowest carbon fraction (24/46 ≈ 0.522).
• D: Propane's carbon fraction (36/44 ≈ 0.818) is less than octane's.

Final answer: C