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 `:`

Options

A. The dissociation energy of `H_(2)` and enthalpy of sublimation of carbon
B. Latent heat of vapourization 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

A

Explanation

`C_((s)) + 2H_(2(g)) to CH_(4(g)) , DeltaH_f^@ = -74.8kJ//mol`
Bond energy of `CH_4` will be the heat of formation of the bond from gaseous atoms constituting the bond with reverse sign.
`C_((g)) + 4H_((g)) to CH_(4(g)), Delta_rH = ?`
`Delta_r H = Delta_f H_(CH_4(g)) - Delta_f H_(C (g)) - Delta_fH_(H(g))`
In this equation the first term is given but the second term `(DeltaH_(C(s) to C(g)))` and third term `(DeltaH_(1/2H_2toH))` are not given.