Energetics & electrochemistry · SL/HL
Bond Enthalpy Calculator
Enter each bond-energy term as “count energy” in kJ mol⁻¹ for bonds broken and formed.
Your values
Start with the example or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or input upload.
Result & working
ExampleThe calculator is loading. The worked example is also shown below.
Step-by-step working
The formula
ΔH ≈ ΣE(bonds broken) − ΣE(bonds formed)
| Symbol | Meaning |
|---|---|
| E | Average bond enthalpy in kJ mol⁻¹. |
When to use this calculator
Average bond enthalpies are gas-phase averages across compounds, so the result is an estimate rather than an exact compound-specific enthalpy.
Worked example
The page opens with these example values. The result below is pre-generated for reference.
- Broken: 1 × 436 = 436 kJ mol⁻¹
- Broken: 1 × 243 = 243 kJ mol⁻¹
- Formed: 2 × 431 = 862 kJ mol⁻¹
- Σ broken = 679; Σ formed = 862
- ΔH ≈ 679 − 862 = -183 kJ mol⁻¹
-183 kJ mol⁻¹
Common mistakes
- Breaking bonds requires energy; forming bonds releases energy in this bookkeeping convention.