Answer:
2COâ‚‚ (g) + 6Hâ‚‚ (g) → CHâ‚OCHâ‚ (g) + 3Hâ‚‚O (â„“)
Now make this reaction up from what you are given:
2 Ă— (COâ‚‚ (g) + 3Hâ‚‚ (g) → CHâ‚OH (l) + Hâ‚‚O (â„“).. â†H° = –131 kJ)
... (2CHâ‚OH (l) → CHâ‚OCHâ‚ (g) + Hâ‚‚O (â„“) .. â†H° = 8kJ)
––––––––––––––––––––––––––––––––––––––... add
2COâ‚‚ (g) + 6Hâ‚‚ (g) → CHâ‚OCHâ‚ (g) + 3Hâ‚‚O (â„“) . - exactly what you want!
â†H° = 2(–131 kJ) + 8 kJ = –254 kJ
