Question

Calculate resonance energy of `C_(6)H_(6) (g)`.
`{:("Given :",Delta_(f)[C_(6)H_(6)(g)]=-360 kJ mol^(-1)),(,DeltaH_("Sub")[C("graphite")]=716 kJ mol^(-1)),(,B.E._(H-H)=437 kJ mol^(-1)),(,B.E._(C=C)=620 kJ mol^(-1)),(,B.E._(C-C)=340 kJ mol^(-1)),(,B.E._(C-H)=490 kJ mol^(-1)):}`

Answer 1

For `C_(6)H_(6)`
`6C(s)+3H_(2)(g) rarr C_(6)H_(6), DeltaH_(exp)=-360" kJ mol"^(-1)`
`:. DeltaH_("cal")" "=-[3 (C-C)+3(C=C)+6(C-H)]+[6C_(S rarr g)+3(H-H)]`
`=-[3xx340+3xx620+6xx490]+[6xx716+3xx437]`
`=- 5820+5607=- 213" kJ mol"^(-1)`
`:.` Resonance energy =Exp. `DeltaH_(f)-` calculated `DeltaH_(f)`
`=-360-(-213)=-360+213 =-147" kJ mol"^(-1)`