Is enthalpy of bond dissociation or heat of bond dissociation endothermic or exothermic?
Answers
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The total enthalpy, H, of a system cannot be measured directly. ... Generally, a positive change in enthalpy is required to break a bond, while a negative change in enthalpy is accompanied by the formation of a bond. In other words, breaking a bond is an endothermic process, while the formation of bonds is exothermic
the strength of the chemical bond between any two species can be estimated with the help of bond dissociation enthalpy. Although it is generally measured as the enthalpy change at standard conditions (298K), the bond dissociation energy of a chemical bond is often defined as the enthalpy change of the homolytic fission of the bond at absolute zero (0K).
Some important features of the concept of bond dissociation enthalpy include:
It is the amount of energy which needs to be supplied in order to break a chemical bond between two species.
It is a means of calculating the strength of a chemical bond.
In diatomic molecules specifically, it is equal to the value of bond energy
The bond between silicon and fluorine is said to have the strongest bond dissociation enthalpy.
Covalent bonds between atoms or molecules are said to have weak bond dissociation energies.
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