Question

The bond energies of `C=C` and `C-C` at `298 K` are `590` and `331 kJ mol^(-1)`, respectively. The enthalpy of polymerisation per mole of ethaylene is
A. `-70kJ`
B. `-72kJ`
C. `72kJ`
D. `-68kJ`

Answer 1

Correct Answer - B
The polymeridation of ethene may be represented as
`nCH_(2)=CH_(2)to[-CH_(2)-CH_(2)-]_(n)`
One mole of C=C bond is decomposed and two moles of C-C bonds are formed per mole of ethane
`thereforeDeltaH=590-2xx331=-72kJ` per mol of ethylene.