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InterviewSolution
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The polymerisation of ethylene to linear polyethylene is represented by the reaction `nCH_(2)=CH_(2)rarr(-CH_(2)-CH_(2)-)_(n)` When `n` has a large integral value. Given theat the average enthalpies of bond dissociation for `C=C` and `C-C` at `298K`are `+590` and `+331kJ mol^(-1)` respectively, calculate the enthalpy of polymerisation per mole of ethylene at `298K`. |
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Answer» `nCH_(2)=CH_(2)to(-CH_(2)-CH_(2)-)_(n)` there are equal number of C-H bonds on both sides but on reactant side there are nC=C bonds and on product side `(2n+1)C-C` bonds. Enthalpy of polymerisation, `=nDeltaH_((C=C))-(2n+1)DeltaH_((C-C))` `=590n-(2n+1)(331)` `=590n-662n` [2n+1`to2n` as n is very large] `=72nkJ` Enthalpy of polymerisation per mole `=(DeltaH)/(n)=(72n)/(n)=72kJ" "mol^(-1)`. |
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