A-LevelChemistryChemical energetics9701/12 · May/June 2015 · Q61 Mark
Metaldehyde, (CH₃CHO)₄, is used as a solid fuel for camping stoves. The equation for the complete combustion of metaldehyde is shown. (CH₃CHO)₄(s) + 10O₂(g) → 8CO₂(g) + 8H₂O(l) ∆Hᶜ = standard enthalpy change of combustion. Which expression will give a correct value for the enthalpy change of formation of metaldehyde?
A∆Hᶜmetaldehyde – (8∆Hᶜcarbon + 8∆Hᶜhydrogen)
B∆Hᶜmetaldehyde – (8∆Hᶜcarbon + 16∆Hᶜhydrogen)
C(8∆Hᶜcarbon + 8∆Hᶜhydrogen) – ∆Hᶜmetaldehyde
D(8∆Hᶜcarbon + 16∆Hᶜhydrogen) – ∆Hᶜmetaldehyde
✓ Correct answer
C: (8∆Hᶜcarbon + 8∆Hᶜhydrogen) – ∆Hᶜmetaldehyde
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