Nimo

Study smarter with Nimo

Personalised revision that adapts to you. Ace your revision with unlimited practice questions that are designed to help you learn faster. We're slowly rolling out to more and more students.

Try Nimo

Calculating energy changes using bond energies

Energy changes • Exothermic and endothermic reactions

Key concepts

What you'll likely be quizzed about

  • Bond energy is the average energy required to break one mole of a specific bond in gaseous molecules, measured in kilojoules per mole (kJ mol−1).
  • These tabulated values are averages across various molecules and bonding environments.
  • Bond energy values serve as approximations, not accounting for variations arising from molecular context, phase, or temperature.

Flashcards

Test your knowledge with interactive flashcards

How do bond energies relate to enthalpies of formation?

Click to reveal answer

Bond-energy calculations estimate reaction enthalpies using bond averages, while enthalpies of formation utilize experimental or calculated absolute enthalpies for species.

Key notes

Important points to keep in mind

List every bond broken and formed from full molecular structures.

Use ΔH = Σ(bond energies broken) − Σ(bond energies formed) with correct multipliers for repeated bonds.

Report answers in kJ mol−1, including the sign for exothermic or endothermic reactions.

Treat tabulated bond energies as averages, expecting deviations from experimental values.

Avoid using covalent bond energy values for ionic lattices or metallic bonds; use appropriate data sources.

Built with v0