Bond Energy Calculator Formula

Understand the math behind the bond energy calculator. Each variable explained with a worked example.

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Formulas Used

Estimated ΔH

delta_h = bonds_broken - bonds_formed

Variables

VariableDescriptionDefault
bonds_brokenTotal Energy of Bonds Broken(kJ/mol)2648
bonds_formedTotal Energy of Bonds Formed(kJ/mol)3466

How It Works

Bond Energy Estimation of ΔH

Formula

ΔH ≈ Σ(bonds broken) − Σ(bonds formed)

Where:

  • Bonds broken = energy required to break all bonds in reactants (positive, endothermic)
  • Bonds formed = energy released forming all bonds in products (positive values)

    • Breaking bonds requires energy; forming bonds releases energy. If more energy is released than absorbed, ΔH is negative (exothermic).

    Worked Example

    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.

    bonds_broken = 2648bonds_formed = 3466
    1. 01ΔH = Σ(bonds broken) - Σ(bonds formed)
    2. 02ΔH = 2648 - 3466
    3. 03ΔH = -818 kJ/mol (exothermic)

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