The enthalpy of atomization for the reaction CH4(g)→C(g)+4H(g) is1665 kj mol−1 What is the bond energy of C−H bond?
Given reaction is
CH4(g)→C(g)+4H(g)
△rH=1665 kj/mol
CH4 contains four C−H bond
∴ To break 4 C−H bond, required energy is 1665 kj/mol.
In methane, all the four C−H bonds are identical in bond length. However, different energies are required to break the individual C−H bonds in each successive step.
Therefore, we can calculate the average bond energy of C−H bond from the given data
∴ Bond enthalpy of C−H = 14(1665)
=416.2 kj/mol