The standard enthalpies of formation of `SO_2` and `SO_3` are -297 `"kJ mol"^(-1)` 396 `"kJ mol"^(-1)` respectively. Calculate the standard enthalpy of reaction for the reaction: `SO_2 + 1//2O_2 to SO_3`

Explanation

Data given ,
(1) `rArr S + O_2 to SO_2 " " DeltaH_f^0=-297 "kJ mol"^(-1)`
(2) `rArr S+ 1 1//2 O_2to SO_3 " " DeltaH_f^0 = -396 "kJ mol"^(-1)`
`SO_2 + 1//2 O_2 to SO_3 " " DeltaH_r` = ?
Equation (1) is reversed and added with equation (2)
`{:(" "SO_2 to cancelS+cancelO_2 " " DeltaH=+297 "kJ mol"^(-1)),(cancelS +cancel1 1/2 O_2 to SO_3 " " DeltaH =-"396 kJ mol"^(-1)),(SO_2+ 1/2 O_2 to SO_3 " " DeltaH_r=+297-396),(" "DeltaH_r=-99 "KJ mol"^(-1)):}`