Per NCERT §5.4(e) (worked example), given C+O₂→CO₂ ΔH = −393.5 and CO+½O₂→CO₂ ΔH = −283.0 kJ/mol, what is Δ_f H° of CO(g)?
A−110.5 kJ/mol
B−393.5 − 283.0 = −676.5 kJ/mol
C+110.5 kJ/mol
D+283.0 kJ/mol
Answer & Solution
Correct answer: A. −110.5 kJ/mol
Per NCERT §5.4(e), reverse (ii) and add to (i): C+½O₂→CO ⇒ Δ_f H° = −393.5 + 283.0 = −110.5 kJ/mol. Matches Table 5.2.
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