The difference between the heats of reaction at constant pressure and a constant volume for the reaction `2C_(6)H_(6)(l) + 15O_(2)(g) rarr 12CO_(2)(g) + 6H_(2)O(l)` at `25^(@)C` in `kJ` is

Explanation

Heat of reaction of constant pressure `(DeltaH)` and heat of reaction at constant volume `(DeltaU)` are related as:
`DeltaH = DeltaU +Deltan_(g)RT`
`:. DeltaH - DeltaU = Deltan_(g)RT`
`Deltan_(g) = 12 - 15 =- 3,R = 8.314 J K^(-1)mol^(-1), T = 298K`
`:. DeltaH - DeltaU =- 3 xx 8.314 xx 10^(-3) xx298 =- 7.43 kJ`