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The term bond-dissociation energy is similar to the related notion of bond-dissociation enthalpy (or bond enthalpy), which is sometimes used interchangeably.However, some authors make the distinction that the bond-dissociation energy (D 0) refers to the enthalpy change at 0 K, while the term bond-dissociation enthalpy is used for the enthalpy change at 298 K (unambiguously denoted DH° 298).
This sum will have a maximum at , representing the point of bond dissociation; summing over all the differences up to this point gives the total energy required to dissociate the molecule, i.e. to promote it from the ground state to an unbound state. This can be written:
The bond energy for H 2 O is the average energy required to break each of the two O–H bonds in sequence: Although the two bonds are the equivalent in the original symmetric molecule, the bond-dissociation energy of an oxygen–hydrogen bond varies slightly depending on whether or not there is another hydrogen atom bonded to the oxygen atom.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
The potential at infinite internuclear distance is the dissociation energy for pure vibrational spectra. For vibronic spectra there are two potential curves (see Figure at right), and the dissociation limit is the upper state energy at infinite distance. Energy level diagram illustrating the Franck–Condon principle.
Bond energy and bond-dissociation energy are measures of the binding energy between the atoms in a chemical bond. It is the energy required to disassemble a molecule into its constituent atoms. This energy appears as chemical energy , such as that released in chemical explosions , the burning of chemical fuel and biological processes.
The dissociation involves cleaving of the molecular bonds in the adsorbate, and formation of new bonds with the substrate. Breaking the atomic bonds of the dissociating molecule requires a large amount of energy, thus dissociative adsorption is an example of chemisorption , where strong adsorbate-substrate bonds are created. [ 1 ]
The heat of dilution can be defined from two perspectives: the differential heat and the integral heat. The differential heat of dilution is viewed on a micro scale, which is associated with the process in which a small amount of solvent is added to a large quantity of solution. The molar differential heat of dilution is thus defined as the enthalpy