Using approximate bond energies, estimate ΔHrxn for the combustion CH4 + 2 O2 → CO2 + 2 H2O. Which value is closest to the correct estimate?

• A. Approximately −808 kJ per mole of CH4 combusted.
• B. Approximately +808 kJ per mole of CH4 combusted.
• C. Approximately −500 kJ per mole of CH4 combusted.
• D. Approximately −1200 kJ per mole of CH4 combusted.

Answer: (A)