To calculate the enthalpy change for the polymerization of polyethylene, we need to find the difference in enthalpy between the reactants and products. In this case, the reactants are ethylene C2H4 and the product is polyethylene [-CH2-CH2-]n .The given enthalpy of formation Hf values are:Hf of ethylene C2H4 = -20.4 kJ/molHf of polyethylene [-CH2-CH2-]n = -1024 kJ/molSince the reaction equation is:nC2H4 g [-CH2-CH2-]n s We can write the enthalpy change H for the reaction as:H = Hf products - Hf reactants However, we need to account for the "n" moles of ethylene in the reaction. So, the equation becomes:H = Hf polyethylene - n * Hf ethylene Now, we can plug in the given values:H = -1024 kJ/mol - n * -20.4 kJ/mol Since we are looking for the enthalpy change per mole of ethylene, we can divide both sides of the equation by "n":H/n = -1024 kJ/mol / n - -20.4 kJ/mol Now, we can simplify the equation:H/n = -1024 kJ/mol + 20.4 kJ/molH/n = -1003.6 kJ/molSo, the enthalpy change for the polymerization of polyethylene is -1003.6 kJ/mol of ethylene.