Chemical Thermodynamics Question 472

Question: The polymerization of ethylene to linear polyethylene is represented by the reaction nCH2=CH2,,(CH2CH2)n when ’n’ has a large integral value. Given that average enthalpies of bond dissociation for C=C and CC at 298 K are + 590 and +331kJmol1 respectively. Then the enthalpy of polymerization/mol of ethylene at298 K is

Options:

A) - 132 kJ

B) - 72 kJ

C) + 80 kJ

D) + 162 kJ

Show Answer

Answer:

Correct Answer: B

Solution:

  • n(CH2=CH2) ,(CH2CH2)n,

ΔH=

Thus, ’n’ double bonds are dissociated to form a molecule with 2n single bonds. ΔH=(nn)(ΣC=C)(2nn)(ΣC=C)

=+,5902×331=72,kJ,mol1



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