Verifying statements using enthalpies of formation Steps:

• Reaction for statements 1 and 3: 2NO(g) + O₂(g) → 2NO₂(g); ΔH = [2 × (+33)] – [2 × (+90)] = 66 – 180 = –114 kJ (exothermic, 57 kJ released per mol NO).
• Statement 1 claims 16 kJ released per mol NO, but calculation shows 57 kJ, so false.
• Decomposition for statement 2: 2NO₂(g) → N₂(g) + 2O₂(g); ΔH = 0 – [2 × (+33)] = –66 kJ (exothermic), so claim of endothermic is false.
• Statement 3 matches the exothermic reaction calculated, so true. Why A is correct:
• A identifies only statement 3 as true, consistent with Hess's law applied to formation enthalpies. Why the others are wrong:
• B includes false statement 1 (wrong energy value).
• C includes false statement 2 (decomposition is exothermic, not endothermic).
• D includes both false statements 1 and 2.

Final answer: A