The enthalpies of combustion of carbon and carbon monoxide are `-390 KJ mol^(-1)` and `-278 KJ mol^(-1)` respectively. The enthalpy of formation of carbon monoxide is 

Explanation

`C _("graphicle") + O _(2 (g)) to CO _(2 (g)) , Delta H =- 393.5 kJ……..(1)`
`CO _((g)) + (1)/(2) O _(2 (g)) to CO _(2 (g)) , Delta H =- 283 Kj ……..(2)`
Equation (1) - equation (2) , gives
`C _(("graphicle")) + (1)/(2) O _(2 (g)) to CO _((g)) ‘ Delta H =-110 .5 kJ`