The polymerization of propylene to polypropylene is represented by: nCH 2 =CH-CH 3 → (-CH 2 -CH(CH 3 )-) n where n has a large integral value. Given that the average bond dissociation enthalpies of C=

Question

The polymerization of propylene to polypropylene is represented by:

nCH₂=CH-CH₃ → (-CH₂-CH(CH₃)-)_n

where n has a large integral value. Given that the average bond dissociation enthalpies of C=C and C-C at 298 K are +614 and +347 kJ/mol, respectively, the enthalpy of polymerization per mole of propylene at 298 K is

TestHub · Accepted Answer

Per mole of propylene, one C=C becomes a C-C bond and one new C-C bond links the unit to the chain; the C-C and C-H bonds of the methyl group are untouched. Net: break 1 C=C, form 2 C-C: ΔH = 614 - 2(347) = -80 kJ per mole of propylene. This is option (c).

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