Question

The standard enthalpy of formation (`DeltaH_(f)^(@))` at `398` K fir methane , `CH_(4(g))` is `748 KJ mol^(-1)`. The additional information required to determine the average energy for `C-H` bond formation would be :
A. the dissociation energy of `H_(2)` and enthalpy fo sublimation of carbon
B. latent heat of vapourisation of methane
C. the first four ionization energies of carbon and electron gain enthalpy of hydrogen
D. the dissociation energy of hydrogen molecule , `H_(2)`

Answer 1

Correct Answer - A
`C=2H_(2) rarr CH_(4), DeltaH^(@) = -74.8 KJ mol^(-1)`
In order to calculate average energy for C-H bond formation we should know the following data. `C("graphite") rarr C(g), DeltaH, `=enthalpy of sublimation of carbon
`H_(2)(g) rarr 2H(g) , DeltaH^(@)` bond dissociation energy of `H_(2)`