Heat of Combustion Calculator
Calculate the heat energy released when burning a fuel. Determinee heat released per gram or per mole from standard enthalpies of combustion.
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Mass of substance in grams
Molar mass (auto-filled for common substances)
What is heat of combustion?
Heat of combustion (ΔH_c) is the energy released when 1 mole of substance burns completely in O₂. Measured in kJ/mol under standard conditions (25°C, 1 atm). Negative ΔH_c means exothermic (heat released). More negative = more energy per mole.
How do you calculate heat released?
q = (mass / M) × ΔH_c. For 10 g methane (M=16.04, ΔH_c = -890.8 kJ/mol): moles = 10/16.04 = 0.623 mol. Heat = 0.623 × (-890.8) = -555 kJ. Heat released = 555 kJ.
What are common heats of combustion?
Hydrogen: -286 kJ/mol (141.9 kJ/g). Carbon: -394 kJ/mol (-32.8 kJ/g). Methane: -891 kJ/mol (-55.5 kJ/g). Gasoline (~C₈H₁₈): ~-5500 kJ/mol (-47 kJ/g). Coal: ~-30 kJ/g. Bomb calorimetry measures these values.
What is the difference between HHV and LHV?
Higher Heating Value (HHV): includes heat from condensing water vapor. Lower Heating Value (LHV): water stays gas. Difference ≈ 44 kJ/mol per H₂O produced (~2.4 kJ/g for hydrocarbons). LHV is used for engine efficiency calculations.