Bond Enthalpy Calculator
Estimate reaction enthalpy from bond energies.
Formula first
Overview
Bond enthalpy measures the energy required to break one mole of a specific chemical bond in the gas phase. The overall enthalpy change of a reaction is determined by the balance between the energy absorbed to break reactant bonds and the energy released when product bonds form.
Symbols
Variables
H = Enthalpy Change, = Energy to Break, = Energy Released
Apply it well
When To Use
When to use: This formula is used to estimate reaction enthalpy for gas-phase reactions when standard enthalpies of formation are unavailable. It assumes that the energy of a specific bond type is relatively constant across different molecular environments.
Why it matters: Predicting whether a reaction is exothermic or endothermic is vital for industrial safety and efficiency. It allows engineers to design cooling systems for high-energy reactions and helps chemists understand the stability of different molecular structures.
Avoid these traps
Common Mistakes
- Subtracting in wrong order.
- Forgetting bonds are averages.
One free problem
Practice Problem
Calculate the enthalpy change for a reaction where the total energy required to break the reactant bonds is 678 kJ/mol and the total energy released during the formation of product bonds is 862 kJ/mol.
Solve for:
Hint: Subtract the energy of bonds formed from the energy of bonds broken.
The full worked solution stays in the interactive walkthrough.
References
Sources
- Atkins' Physical Chemistry (11th ed.)
- IUPAC Gold Book: Bond energy
- IUPAC Gold Book: Enthalpy of reaction
- Wikipedia: Bond-dissociation energy
- IUPAC Gold Book
- Atkins' Physical Chemistry
- NIST Chemistry WebBook
- NIST CODATA