Question

Match the extra element present in the organic compound with reagent used for its detection.

• A. A-IV, B-I, C-II, D-III
• B. A-IV, B-III, C-II, D-I
• C. A-III, B-I, C-IV, D-II
• D. A-III, B-IV, C-I, D-II

Hint:

Lassaigne Test: Nitrogen → Ferrous sulphate, Sulphur → Sodium nitroprusside, Halogen → Silver nitrate, Phosphorus → Ammonium molybdate.

Answer 1

The Correct Option is B

Concept: Extra elements in organic compounds are detected mainly through

Lassaigne's test. Sodium fusion converts covalently bonded elements into ionic compounds which can be detected by characteristic reagents. Different reagents detect different elements.

Step 1: Detection of nitrogen. Nitrogen forms sodium cyanide. It reacts with ferrous sulphate followed by acidification. Reagent used: \[ FeSO_4|H^+ \] Thus \[ N\rightarrow C \]

Step 2: Detection of sulphur. Sulphur forms sodium sulphide. Detected by sodium nitroprusside. \[ Na_2[Fe(CN)_5NO] \] Thus \[ S\rightarrow D \]

Step 3: Detection of chlorine. Halogens react with silver nitrate. \[ AgNO_3 \] Thus \[ Cl\rightarrow B \]

Step 4: Detection of phosphorus. Phosphorus forms phosphate. Detected using ammonium molybdate. \[ (NH_4)_2MoO_4 \] Thus \[ P\rightarrow A \] Final matching: \[ A-IV,\qquad B-III,\qquad C-I,\qquad D-II \] Hence answer: \[ \boxed{B} \]