# The standard enthalpy of formation $\;(\bigtriangleup_{f}H_{298}^{o})\;$ for methane, $\;CH_{4}\;$ is $\;-74.9\;kJmol_{-1}\;$.In order to calculate the average energy given out in the formation of a C - H bond from this it is necessary to know which one of the following ?

(a) The dissociation energy of the hydrogen molecule,$\;H_{2}\;$(b) The first four ionisation energies of carbon(c) The dissociation energy of $\;H_{2}\;$ and enthalpy of sublimation of carbon (graphite)(d) The first four ionisation energies of carbon and electron affinity of hydrogen