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

Step 1: Recall the detection method.
Extra elements such as N, S, halogens, and P are detected after sodium fusion (Lassaigne's test), which turns covalent elements into ionic species.
Step 2: Match nitrogen.
Fused nitrogen gives sodium cyanide, detected by adding ferrous sulphate and then acidifying to form Prussian blue, so nitrogen pairs with the $\text{FeSO}_4$/$\text{H}^+$ reagent.
Step 3: Match sulphur.
Sulphur becomes sodium sulphide, detected by sodium nitroprusside giving a purple colour.
Step 4: Match the halogen.
Chlorine becomes sodium halide, detected by silver nitrate giving a precipitate.
Step 5: Match phosphorus.
Phosphorus becomes phosphate, detected by ammonium molybdate giving a yellow precipitate.
Step 6: Read off the matching.
Combining these pairings reproduces the option A-IV, B-III, C-II, D-I, which is option 2.
\[ \boxed{\text{A-IV, B-III, C-II, D-I}} \]