NEETChemistryGeneral Organic Chemistry
Match List-I with List-II regarding Lassaigne's test for organic compounds: List-I (Elements present) List-II (Observation) (A) Nitrogen (I) Blood red colour with Fe ³⁺ (B) Sulphur (II) Violet colour with sodium nitroprusside (C) Both Nitrogen and Sulphur (III) Prussian blue colour with FeSO ₄ and conc. H ₂ SO ₄ (D) Chlorine (IV) White precipitate with AgNO ₃ soluble in NH ₄ OH Choose the correct answer from the opti
Options
- A(A)-(I), (B)-(II), (C)-(III), (D)-(IV)
- B(A)-(III), (B)-(II), (C)-(I), (D)-(IV)
- C(A)-(III), (B)-(I), (C)-(II), (D)-(IV)
- D(A)-(II), (B)-(III), (C)-(I), (D)-(IV)
Correct answer
B. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
Step-by-step solution
In Lassaigne's test for organic compounds: Nitrogen forms sodium cyanide ( NaCN ), which reacts with FeSO ₄ and conc. H ₂ SO ₄ to give a Prussian blue colour of Fe ₄[ Fe ( CN )₆]₃ . Sulphur forms sodium sulphide ( Na ₂ S ), which gives a violet colour with sodium nitroprusside due to the formation of [ Fe ( CN )₅ NOS ]⁴⁻ . When both Nitrogen and Sulphur are present, sodium thiocyanate ( NaSCN ) is formed, which gives a blood red colour with Fe ³⁺ ions due to the formation of [ Fe ( SCN )]²⁺ . Chlorine forms sodium