Answer:
Average molar bond enthalpy of C-H bond in [tex]CH_{4}[/tex] is 415.825 kJ/mol.
Explanation:
Reaction: [tex]CH_{4}(g)\rightarrow C(g)+4H(g)[/tex]
Heat of reaction (energy needed to break 4 moles of C-H bond in 1 mol of [tex]CH_{4}[/tex]) = [tex]\Delta H^{0}=[1mol\times \Delta H_{f}^{0}(C)_{g}]+[4mol\times \Delta H_{f}^{0}(H)_{g}]-[1mol\times \Delta H_{f}^{0}(CH_{4})_{g}][/tex]
= [tex][1mol\times 716.7\frac{kJ}{mol}]+[4mol\times 218.0\frac{kJ}{mol}]-[1mol\times -74.6\frac{kJ}{mol}]=1663.3kJ[/tex]
1 mol of [tex]CH_{4}[/tex] contain 4 moles of C-H bonds.
So, average molar bond enthalpy of C-H bond in [tex]CH_{4}[/tex]
= [tex]\frac{1663.3}{4}kJ/mol[/tex]
= 415.825 kJ/mol
