Question

Calculate the enthalpy change for the polymerization reaction of ethylene to form polyethylene using the bond dissociation energies listed below: C-H bond energy = 413 kJ/mol C=C bond energy = 602 kJ/mol Assume that the polymerization reaction proceeds via breaking of the C=C bond followed by formation of the C-C bond in polyethylene.

Answer 1

To calculate the enthalpy change for the polymerization reaction of ethylene to form polyethylene, we need to consider the bond dissociation energies of the bonds being broken and formed during the reaction.In the polymerization reaction, the C=C bond in ethylene is broken, and a new C-C bond is formed in the polyethylene chain. The bond dissociation energies for the C=C bond and the C-C bond are given as:C=C bond energy = 602 kJ/molWe also need the bond dissociation energy for the C-C bond. The average bond dissociation energy for a C-C single bond is approximately 348 kJ/mol.Now we can calculate the enthalpy change  H  for the reaction using the bond dissociation energies:H =  Energy of bonds broken  -  Energy of bonds formed H =  C=C bond energy  -  C-C bond energy H =  602 kJ/mol  -  348 kJ/mol H = 254 kJ/molThe enthalpy change for the polymerization reaction of ethylene to form polyethylene is 254 kJ/mol.