Given: (i) C(graphite) + O2(g) CO2(g); H = x (ii) C(graphite) + 12O2(g) CO(g); H = y (iii) CO(g) + 12O2(g) CO2(g); H =…
Thermodynamics · Class 11 · JEE Main Previous Year Question
Given: (i) (ii) (iii)
Which algebraic relationship is correct?
- a✓
- b
- c
- d
🧠 Hess's Law: two routes to the same product must give the same total enthalpy can be made from carbon in two steps (via CO) or in one step directly. Both paths start at the same point and end at the same point.
🗺️ Applying Hess's Law Route 1 (direct): ,
Route 2 (two steps): (), then ().
Since both routes start and end at the same state:
This is just Hess's Law — the sum of the two-step route equals the single-step route.
⚠️ Trap: Options (b)–(d) rearrange the terms incorrectly. Only (a) correctly adds the two steps to give the direct route.
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