Use bond energies to estimate the enthalpy change for the reaction of one mole of CH₄ with chlorine gas to give CH₃Cl and hydrogen chloride.
BE(C-H) = 414 kJ/mol
BE(C-Cl) = 326 kJ/mol
BE(H-Cl) = 432 kJ/mol
BE(Cl-Cl) = 243 kJ/mol

Question

Quizplus · Accepted Answer

The enthalpy change is calculated by subtracting the total bond energies of products from the total bond energies of reactants. Breaking bonds: 1 C-H (414 kJ/mol) and 1 Cl-Cl (243 kJ/mol) = 657 kJ/mol. Forming bonds: 1 C-Cl (326 kJ/mol) and 1 H-Cl (432 kJ/mol) = 758 kJ/mol. Enthalpy change = 657 - 758 = -101 kJ/mol.

Use Bond Energies to Estimate the Enthalpy Change for the Reaction