Answer:
- 228.6 kJ/mol.
Explanation:
∵ ΔGrxn = ∑ΔGf, products - ∑ΔGf, reactants
<em>4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O, </em>
∴ ΔGrxn = [6(ΔGf, H₂O) + 4(ΔGf, NO)] - [4(ΔGf, NH₃) + 5(ΔGf, O₂)]
ΔGrxn = – 957.9 kJ, ΔGf, H₂O = ??? KJ/mol, ΔGf, NO = 86.71 kJ/mol, ΔGf, NH₃ = - 16.66 kJ/mol, ΔGf, O₂ = 0.0 kJ/mol.
∴ – 957.9 kJ = [6(ΔGf, H₂O) + 4(86.71 kJ/mol)] - [4(- 16.66 kJ/mol) + 5(0.0 kJ/mol)].
– 957.9 kJ = 6(ΔGf, H₂O) + 346.8 kJ/mol + 66.64 kJ/mol
– 957.9 kJ = 6(ΔGf, H₂O) + 413.8 kJ/mol
6(ΔGf, H₂O) = – 957.9 kJ - 413.8 kJ/mol = - 1372 kJ/mol.
<em>∴ ΔGf, H₂O</em> = (- 1372 kJ/mol)/6 = <em>- 228.6 kJ/mol.</em>
