Given that `C+O_(2)rarrCO_(2),DeltaH^(@)=-xKJ` and `2CO+O_(2)rarr2CO_(2),DeltaH^(@)=-yKJ` The enthalpy of formation of carbon monoxide will be

Options

A. `y-2x`
B. `2x-y`
C. `(y-2x)/(2)`
D. `(2x-y)/(2)`

Answer

C

Explanation

`C + O_(2) to CO_(2),`
`DeltaH^(@) =- x KJ` …(i)
ON reversing given second equation we get,
`2CO_(2) to 2CO + O_(2) , DeltaH^(@) = + y KJ`
or `CO_(2) to CO + 1//2O_(2), DeltaH^(@) =+ y//2 KJ " "…(ii)`
From Eqs. (i) and (ii) (by additon)
`C+(1)/(2)O_(2) to CO,`
`DeltaH^(@) =(y)/(2) -x =(y-2x)/(2) KJ`