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Chemical Bonds

Chemistry: Edexcel IGCSE, topic 14.1.10

Chemical Bonds

All chemical bonds have a "bond energy" that measures the strength of chemical bonds. By subtracting the total bond energies of the products from the total bond energies of reactants, we can see if a reaction is endothermic or exothermic (energy change in kJ mol-1).

Exothermic reactions

Exothermic reactions

  • Energy released by forming bonds > energy required to break bonds.
  • I.e. overall energy change of reaction < 0.
Endothermic reactions

Endothermic reactions

  • Energy released by forming bonds < energy required to break bonds.
  • I.e. overall energy change of reaction > 0.

Test yourself on Chemical Bonds

  • What is the most commonly used unit for measuring bond energies?

  • Which of these are true about bond making and breaking?

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