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JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Practical and Analytical Chemistry

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Lassaigne's test is used for detection of :
  1. (A)Nitrogen and Sulphur only
  2. (B)Nitrogen, Sulphur and Phosphorous Only
  3. (C)Phosphorous and halogens only
  4. (D)Nitrogen, Sulphur, phosphorous and halogens✓ Correct

Answer: (D)

Solution

In Lassaigne's (sodium fusion) test, an organic compound is fused with sodium metal, converting covalently bound heteroatoms into water-soluble sodium salts: nitrogen becomes NaCN (detected by the Prussian blue test), sulphur becomes (detected by the sodium nitroprusside or lead acetate test), phosphorus becomes (detected by the ammonium molybdate test), and halogens become NaX (detected by the silver nitrate test after acidification). The test therefore detects nitrogen, sulphur, phosphorus, and halogens together.

JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Single correct option

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