Consider the following data: _ f H ^ (methane, g )=- X kJ mol ⁻¹ Enthalpy of sublimation of graphite = Y kJ mol ⁻¹ Dissociation enthalpy of H ₂= Z kJ mol ⁻¹ The bond enthalpy of C - H bond is given by :

Step-by-step solution

For methane formation: C(g) + 2 H ₂(g) CH ₄(g) . Using enthalpy balance: _f H° = Bonds broken - Bonds formed . Breaking: sublimation of C (Y) and 2 H-H bonds (2Z); Forming: 4 C-H bonds. Energy equation: -X = Y + 2Z - 4B where B is C-H bond enthalpy. Solving: 4B = X + Y + 2Z , so B = X + Y + 2Z 4 .