Enthalpy of Formation of Carbon Monoxide

[SherlockOhms]

Homework Statement

Using the information provided for energy changes associated with the formation
of carbon dioxide, calculate the enthalpy for the formation of carbon monoxide.

C(gr) + O2(g) → CO2(g) ΔH (-393.5 kJ mol-1)
CO(g) + ½ O2 (g) → CO2 (g) ΔH (-283 kJ mol -1)
C(gr) + ½ O2 (g) → CO(g) ΔH = ?

Homework Equations

None really.

The Attempt at a Solution

Reverse equation #2 to get CO2 (g) → CO(g) + ½ O2 (g) (+283 kJ mol -1). I think that's one of the steps anyway. Haven't done of these in ages. Do I sub in for CO2 in equation #1 and then add the enthalpy of formations? What's the next step?

 

[Borek]

Combine first two equations in such a way they yield third.

 

[SherlockOhms]

Thanks for that.