The standard enthalpy of formation (ΔfH°) at 298 K for methane, CH4(g), is -74.8 kJ mol -1. The additional information required to determine the average energy for C—H bond formation would be:

Question

The standard enthalpy of formation (ΔfH°) at 298 K for methane, CH4(g), is -74.8 kJ mol -1. The additional information required to determine the average energy for C—H bond formation would be: (A) The dissociation energy of hydrogen molecule, H2 (B) The dissociation energy of H2 and enthalpy of sublimation of carbon (C) Latent heat of vaporisation of methane (D) The first four ionisation energies of carbon and electron gain enthalpy of hydrogen

Tardigrade Admin · Accepted Answer

C + 2H2→ CH4 ΔfH°=[eC(s→ g)+2× eH-H-4× eC-H]

Q. The standard enthalpy of formation $(Δ_{f} H^{\circ})$ at $298 K$ for methane, $C H_{4} (g)$ , is $- 74.8 k J$ mol $^{- 1}$ . The additional information required to determine the average energy for $C — H$ bond formation would be:

The dissociation energy of hydrogen molecule, $H_{2}$

The dissociation energy of $H_{2}$ and enthalpy of sublimation of carbon

Latent heat of vaporisation of methane

The first four ionisation energies of carbon and electron gain enthalpy of hydrogen

$C + 2 H_{2} \to C H_{4}$
$Δ_{f} H^{\circ} = [e_{C (s \to g)} + 2 \times e_{H - H} - 4 \times e_{C - H}]$

Q. The standard enthalpy of formation (Δf​H∘) at 298K for methane, CH4​(g), is −74.8kJ mol −1. The additional information required to determine the average energy for C—H bond formation would be:

The dissociation energy of hydrogen molecule, H2​

The dissociation energy of H2​ and enthalpy of sublimation of carbon