The standard enthalpy of formation of CH ₄ , the standard enthalpy of sublimation of Carbon and the bond dissociation enthalpy of Hydrogen gas are -74.8,+719.6 and 436 ~kJ / mol respectively. What is the bond enthalpy of C - H bond in Methane?

Step-by-step solution

The formation reaction of methane is given by: C(s) + 2 H ₂ (g) CH ₄ (g) . The enthalpy of this reaction is _f H^ = -74.8 kJ/mol . The atomization process involves the sublimation of carbon and the dissociation of hydrogen molecules: 1. C(s) C(g) , H₁ = 719.6 kJ/mol 2. 2 H ₂ (g) 4 H(g) , H₂ = 2 436 = 872 kJ/mol The total energy required to break all bonds in CH ₄ to form gaseous atoms is the enthalpy of atomization of methane, _ at H^ : _ at H^ = H₁ + H₂ - _f H^ _ at H^ = 719.6 + 872 - (-74.8) = 719.6 + 872 + 74.8