Question

The standard enthalpy of formation `(Delta_(f)H^(@))` at `298K ` for methane `(CH_(4(g)))` is `-74.8kJ mol^(-1)`. The additional information required to determine the average energy for `C-H` bond formation would be `:`
A. The first four ionization of carbon and electron gain enthalpy of hydrogen
B. The dissociation energy of hydrogen molecule `H_(2)`.
C. The dissociation energy of `H_(2)` and enthlpy of sublimation of carbon
D. latent heat of vaporisation of methane.

Answer 1

Correct Answer - C
Given `C("graphite")+2H_(2)(g)toCH_(4)(g)`, `DeltaH=-71.8 kJ mol^(-1)`
Aim `(1)/(4)[CH_(4)(g)toC(g)+4H(g)`, `DeltaH=? `
Hence to calculate average `DeltaH` for `C-H` bond, we require dissociation energy of `H_(2)` and enthalpy of sublimation of carbon.