The following two reaction are known :-
`N_(2(g))+O_(2(g))hArr2NO_((g)),DeltaH=-27.1KJ`
`2N_(2(g))+O_(2(g))hArr2NO_(2(g)),DeltaH=-53.5KJ`
Calculate the enthalpy change for the reaction
`NO_(2(g))hArr(1)/(2)N_(2(g))+O_(2(g))`

Options

A. `-40.3KJ`
B. `+80.6KJ`
C. `+40.3KJ`
D. `-80.6KJ`

Answer

C

Explanation

`(3)=-(1)/(2)xx(1)-(1)/(2)xx(2)`
`=-(1)/(2)xx(-27.1)-(1)/(2)(-53.5)`
`DeltaH.=+40.3KJ`