A Level Chemistry OCR Practice Exam

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What does bond enthalpy refer to?

The energy required to form a bond
The enthalpy change for breaking a mole of a bond
The total energy of all bonds in a molecule
The average strength of bonds in a molecule

The correct answer is: The enthalpy change for breaking a mole of a bond

Bond enthalpy specifically refers to the enthalpy change associated with breaking one mole of a specific type of bond in a gaseous substance. It is a measure of the energy required to break that bond, indicating how strong the bond is. When considering the energy needed to break a bond, researchers look at this in the context of the energy absorbed during the process, which translates to the strength of the bond being evaluated. The concept focuses on the breaking of bonds rather than their formation or the general energy of all bonds in a molecule. Therefore, considering bond enthalpy allows chemists to quantify the strength of a given bond within a molecule, which is essential for understanding reactivity and stability in chemical reactions. This makes the correct answer aligned with the definition and application of bond enthalpy in thermochemical calculations and molecular analysis.