Question

The dissociation energy of methane and ethane are 360 and 620kcalmol$^{-1}$. The value of ${{e}_{c-c}}$ in kcal mol$^{-1}$ is_

Answer 1

Hint: Chemical and biochemical dissociation is a general mechanism in which molecules (or ionic compounds such as salts or complexes) differentiate or break into smaller particles such as atoms , ions, or radicals, typically reversibly.For example, when an acid dissolves in water, the heterolytic fission breaks a covalent bond between an electronegative atom and a hydrogen atom which gives a proton (${{H}^{+}}$) and a negative ion.

Complete answer:
The enthalpy of bond dissociation is the energy necessary to split one mole of the bond to give separate atoms. In the case of methane, 360 kcal / mol energy is required to break a mole of methane gas into gaseous carbon and hydrogen atoms, and 4 moles of C-H bonds are broken.
Therefore, the average energy of the bond is $\dfrac{360}{4}$ kcal/mol, which is 90 kcal per mole of bonds. In case of ethane,
$\begin{align}
  & 6(C-H)+C-C=620 \\
 & 6\times 90+C-C=620 \\
\end{align}$
${{e}_{c-c}}$=620−540=80kcal/mol
The bond-separation vitality is one proportion of the quality of a compound bond A–B. It tends to be characterized as the standard enthalpy change when A–B is severed by homolysis to give sections A and B, which are normally radical species.

Note:
-The enthalpy change is temperature-subordinate, and the bond-separation vitality is regularly characterized to be the enthalpy change of the homolysis at 0 K (supreme zero), despite the fact that the enthalpy changes at 298 K (standard conditions) is additionally an oftentimes experienced boundary
- Dissociation is the opposite of merging or recombining.