The enthalpy of atomisation for the reaction CH4(g)→ C(g) + 4H (g) is 1665 kJ mol–1. What is the bond energy of the C–H bond?
o Enthalpy of atomisation is defined as The enthalpy of atomization is the enthalpy change related to the total separation of all atoms in a chemical substance (either of a chemical element or of a chemical compound).
o For the given reaction CH4(g)→C(g) + 4H (g), the enthalpy of atomisation ∆aHΘ =1665 kJ mol –1.
o And it can be seen that the decomposition of methane is occurring by the breakage of 4 C-H bonds Present in methane.
Hence, for 1 C-H bond, the bond energy will be equal to 1/4 that of the enthalpy of atomisation
= (1665/4) = 416.25 kJ mol–1 .