What is the Difference Between Enthalpy of Atomisation and Bond Dissociation?
🆚 Go to Comparative Table 🆚The primary difference between the enthalpy of atomisation and bond dissociation lies in the processes they describe:
- Enthalpy of Atomisation: This is the energy required to separate a molecule into its atoms. During the process of atomisation, all types of chemical bonds are broken down, and none are formed. The enthalpy of atomisation is always a positive value.
- Bond Dissociation Enthalpy: This is the energy required to break a particular bond in a molecule. For example, in a methane molecule (CH4), there are 4 C-H bonds, and the bond dissociation enthalpy would be the energy needed to break a single C-H bond.
While these terms can be used interchangeably for some simple compounds, they differ most of the time. The enthalpy of atomisation describes the energy required to break all bonds in a molecule, while bond dissociation enthalpy refers to the energy needed to break a specific bond within a molecule.
Comparative Table: Enthalpy of Atomisation vs Bond Dissociation
The main difference between enthalpy of atomisation and bond dissociation lies in the processes they describe. Here is a comparison table highlighting the differences:
| Feature | Enthalpy of Atomisation | Bond Dissociation Enthalpy |
|---|---|---|
| Definition | The energy required to separate a chemical substance into its individual atoms, breaking all chemical bonds | The energy required to break a specific chemical bond in a molecule |
| Symbol | ΔHat | DH0 |
| Units | kJ/mol | kJ/mol |
| Process | Separating a mole of compound into its atom parts, breaking all chemical bonds | Breaking a single bond, such as C-H in a methane molecule |
| Example | CH4(g) -> C(g) + 4H(g) (where the enthalpy of atomisation for this reaction is 1665 kJ/mol) | H2(g) -> 2H(g): Bond dissociation enthalpy of H2(s) is 436.0 kJ/mol |
In summary, enthalpy of atomisation is the energy required to break all chemical bonds in a compound and separate it into individual atoms, while bond dissociation enthalpy is the energy required to break a specific chemical bond in a molecule.
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