Enthalpies: formation, combustion, neutralization, solution, lattice, bond
Chemical Thermodynamics · Chemistry
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Estimate ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O using bond enthalpies. (C–H 413, O=O 498, C=O 799, O–H 463 kJ/mol) Step 1: Broken: 4 C–H + 2 O=O = 4(413) + 2(498) = 2648 kJ. Step 2: Formed: 2 C=O + 4 O–H = 2(799) + 4(463) = 3450 kJ. Step 3: ΔH ≈ broken − formed = 2648 − 3450 = −802 kJ. Step 4: Tabulated ΔH_c° = −890 kJ — bond enthalpies are averages, so estimate only.