Given (a) C(s) + O₂(g) → CO₂(g), ΔH = -394 kJ; (b) CO(g) + ½O₂(g) → CO₂(g), ΔH = -283 kJ. What is ΔH for C(s) + ½O₂(g) → CO(g)?
Answer and explanation
Correct answer: B. -111 kJ
- Step 1: The target equation equals (a) - (b).
- Step 2: ΔH values combine in the same way: ΔH = -111 kJ.
Answer
-111 kJ.
Why not the others: -677 kJ: the two values were added, but (b) has to be reversed. 111 kJ: the sign is reversed. -394 kJ: only equation (a) was used.
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