Chemistry - Thermochemistry Question with Solution | TestHub
The polymerization of ethylene to linear polyethylene is represented by the reaction:
nCH2=CH2 → (-CH2-CH2-)n
where n has a large integral value. Given that the average enthalpies of bond dissociation for C=C and C-C at 298 K are +590 and +331 kJ/mol, respectively, the enthalpy of polymerization per mole of ethylene at 298 K is
Options:
Answer:
Solution:
Per mole of ethylene, the C=C bond converts to a C-C bond, and one new C-C linkage forms between adjacent units. Therefore, the net change involves breaking one C=C bond and forming two C-C bonds.
The enthalpy change (Δ H) can be calculated as follows:
Δ H = (Energy to break 1 C=C bond) - (Energy to form 2 C-C bonds)
Δ H = 590 kJ/mol - 2(331 kJ/mol)
Δ H = 590 kJ/mol - 662 kJ/mol
Δ H = -72 kJ/mol
This corresponds to option (a).
