Reactions which will give $[\mathrm{NO}]^{+}$ as a major product are:
(a)A and B
(b)C and D
(c)A and C
(d)B and D
Answer
Answer: B ✓ checked by 4AB · confidence high
The source book printed D; on checking, B is correct — see the explanation.
The printed key (b), C and D, is restored. NOCl + SbCl5 → [NO]⁺[SbCl6]⁻ and NOCl in BrF3 → [NO]⁺[BrF4]⁻ both give the nitrosonium ion. NOCl + AgNO3 is the N2O4 solvent-system neutralisation, giving AgCl + molecular N2O4 with no NO⁺ salt. The earlier change to (d), B and D, rested on calling N2O4 'NO⁺NO3⁻', which is wrong.
Explanation
In the N₂O₄ solvent system (N₂O₄ ⇌ NO⁺ + NO₃⁻), NOCl is an acid, i.e. an NO⁺ donor. (A) With the metal Sn it behaves like H⁺ with a metal: Sn is oxidised to a chloride and NO⁺ is reduced to neutral NO, so NO⁺ is not the product. (B) NOCl + AgNO₃ → AgCl↓ + N₂O₄ is an acid–base neutralisation in this solvent system. Its product is molecular N₂O₄, not an NO⁺ salt. (C) In BrF₃, NOCl is fluorinated and gives the nitrosonium salt [NO]⁺[BrF₄]⁻. (D) The Lewis acid SbCl₅ abstracts Cl⁻: NOCl + SbCl₅ → [NO]⁺[SbCl₆]⁻. Reactions C and D give [NO]⁺ as the major product, so the answer is option (b).