Free Bond Energy Calculator
Estimate the enthalpy change of a reaction from the total bond energies broken in reactants minus bonds formed in products.
kJ/mol
kJ/mol
Estimated ΔH
-818.0 kJ/mol
Estimated ΔH vs Total Energy of Bonds Broken
Bond Energy Estimation of ΔH
Formula
ΔH ≈ Σ(bonds broken) − Σ(bonds formed)
Where:
Breaking bonds requires energy; forming bonds releases energy. If more energy is released than absorbed, ΔH is negative (exothermic).
Example Calculation
Combustion of CH₄: bonds broken = 4(C-H) + 2(O=O) = 4(413) + 2(498) = 2648 kJ; bonds formed = 2(C=O) + 4(O-H) = 2(805) + 4(464) = 3466 kJ.
- 01ΔH = Σ(bonds broken) - Σ(bonds formed)
- 02ΔH = 2648 - 3466
- 03ΔH = -818 kJ/mol (exothermic)
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