Chemistry - Thermochemistry - Bond enthalpies - Bond Enthalpy Calculations

3 worked examples. Example 1: 'Find ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O using bond enthalpies. Bonds broken: 4×C-H (4×413=1652) + 2×O=O (2×498=996) = 2648 kJ. Bonds made: 2×C=O (2×804=1608) + 4×O-H (4×464=1856) = 3464 kJ. ΔH = 2648 - 3464 = -816 kJ/mol.' (Actual: -891, showing it's approximate). Example 2