Anion identification and redox analysis in NH₄NO₃ decomposition

Steps:

• Identify the anion in NH₄NO₃: it dissociates into NH₄⁺ (cation) and NO₃⁻ (anion), so gap 1 is NO₃⁻.
• Determine oxidation states: N in NH₄⁺ is -3; N in NO₃⁻ is +5.
• Analyze products in the decomposition (considering balanced form 2NH₄NO₃ → 2N₂ + O₂ + 4H₂O): N₂ has N at 0, so N from NH₄⁺ oxidizes (-3 to 0) while N from NO₃⁻ reduces (+5 to 0).
• Conclude gap 2 is NH₄⁺, as its nitrogen atoms are oxidized.

Why C is correct:

• C provides NO₃⁻ for the anion (gap 1) and NH₄⁺ (gap 2) for the oxidized nitrogen, matching the redox roles per oxidation state changes.

Why the others are wrong:

• A: NH₄⁺ is the cation, not anion, for gap 1; NH₂ is unrelated to the reaction.
• B: NO₃⁻ correct for gap 1, but its N is reduced, not oxidized, for gap 2.
• D: NO₃⁻ correct for gap 1, but NO₂⁻ implies nitrite, absent in the decomposition or oxidation.

Final answer: C