The polymerisation of ethylene to linear polyethylene is represented by the reaction, `nCH_(2)= CH_(2) rarr (- CH_(2) - CH_(2) -)` where n has a large integral value. Given that the average enthalpies of bond dissociation for`C=C` and`C-C` at298 K are`+590` and`+331kJ mol^(-1)` respectively, calculate the enthalpy of polymerisation per mole of ethyleneat298 K.

The polymerisation of ethylene to linear polyethylene is represented b

1.	The polymerisation of ethylene to linear polyethylene is represented by the reaction, `nCH_(2)= CH_(2) rarr (- CH_(2) - CH_(2) -)` where n has a large integral value. Given that the average enthalpies of bond dissociation for`C=C` and`C-C` at298 K are`+590` and`+331kJ mol^(-1)` respectively, calculate the enthalpy of polymerisation per mole of ethyleneat298 K.
Answer» In the given polymerisation reaction,one molecule of ethylene involves breaking of C`=` C double bond and formation of threeC-C single bonds.However,in the complete polymer chain,the number of single C-C bonds formedin two per C=C double bond broken Energy required in breaking of one moleofC=C doublebonds `= 590 kJ` Energy released in the formation of two moles of`C-C` single bonds `= 2 xx 331 = 662kJ` `:.`Net energy released per moleof ethylene `= 662 - 590 = 72 kJ , i.e.,DeltaH =- 72kJ mol^(-10`

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