What is the enthalpy change for the combustion of 1.0 mol of methane (CH₄), given: ΔHf (CH₄) = -74.8 kJ/mol, ΔHf (CO₂) = -393.5 kJ/mol, ΔHf (H₂O) = -285.8 kJ/mol? (CH₄ + 2O₂ → CO₂ + 2H₂O)
Correct answer: A. -890.3 kJ
- A. -890.3 kJ
- B. -604.5 kJ
- C. -445.1 kJ
- D. -668 kJ
Explanation
ΔHrnx = ΣΔHf (products) - ΣΔHf (reactants) = [-393.5 + 2(-285.8)] - [-74.8] = -890.3 kJ.
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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