Question

Match the organic compounds in column - I with the Lassaigne's test results in column - II appropriately :

Column - I	Column - II
(A) Aniline	(i) Red color with \(\mathrm{FeCl_3}\)
(B) Benzene sulfonic acid	(ii) Violet color with sodium nitroprusside
(C) Thiourea	(iii) Blue color with hot and acidic solution of \(\mathrm{FeSO_4}\)

• (A) - (ii) ; (B) - (i) ; (C) - (iii)
• (A) - (iii) ; (B) - (ii) ; (C) - (i)
• (A) - (ii) ; (B) - (iii) ; (C) - (i)
• (A) - (iii) ; (B) - (i) ; (C) - (ii)

Hint:

Decide which of N, S or both are present in each compound: N alone gives Prussian blue, S alone gives violet with nitroprusside, N and S together give blood red with FeCl3.

Answer 1

The Correct Option is B

Lassaigne extract tests:
Nitrogen only: sodium cyanide, then hot acidic \(\mathrm{FeSO_4}\) gives Prussian blue colour. Aniline (N only) matches (A) - (iii).
Sulphur only: sodium sulphide gives violet colour with sodium nitroprusside. Benzenesulfonic acid contains S but no N, so (B) - (ii).
Nitrogen and sulphur both: sodium thiocyanate gives blood red colour with \(\mathrm{FeCl_3}\). Thiourea \(\mathrm{(NH_2)_2CS}\) has both, so (C) - (i).
Combination: (A)-(iii), (B)-(ii), (C)-(i).
Answer: (2) (A) - (iii) ; (B) - (ii) ; (C) - (i)