a. Why are alkanes inert ?
b. Why the (C----C) bond rather than (C----H) bond breaks when alkanes are pyrolysed ?
c. Why the combustion of alkanes does not occur at moderate temperature, although it is an exothermic process ?

Explanation

a. Alkanes do not have reactive sites and therefore are inert. A reactive site in a molecule must have:
I. One or more unshared pair of `bar e`'s
ii. A polar bound
iii. An `bar e`-deficient atom or
iv. an atom with an expandable octet
However, alkanes have none of them.
b. The (C----C) bond has a lower bond energy `(Delta H= + 347 kJ mol^(-1))` than (C----H) bond `(Delta H= 415 kJ mol^(-1)`.
c. Since the energy of activation `(Delta H_(act))` is very high, the reaction is very slow at room temperature.