The standared heat of formation listed for gaseous `NH_(3)` is `-11.0kcal mol^(-1)` at `298K`. Given that at `298k`, the constant pressure heat capacities of gaseous `N_(2),H_(2)`, and `NH_(3)` are, respectively, `7.0, 6.0` and `8.0 cal mol^(-1)`. Determine `DeltaH^(Theta)underset(298K)` and `DeltaH_(773K)` for the reactions:
`(1)/(2)N_(2)(g) +(3)/(2)H_(2)(g) rarr NH_(3)(g)`

Explanation

`(1)/(2)N_(2)(g)+(3)/(2)H_(2)(g)toNH_(3)(g)`
`DeltaH_(298K)=sum(H_(f))_(P)-sum(H_(f))_(R)=(-11.02-0)=-11.02kcal" "mol^(-1)`
`(DeltaH_(2)-DeltaH_(1))/(T_(2)-T_(1))=DeltaC_(P)`
`(DeltaH_(2)-(-11.02))/(773-298)=(8.38-(1)/(2)xx6.96-(3)/(2)xx6.89)xx10^(-3)`
`DeltaH_(2)=-13.6" kcal "mol^(-1)`.