DISTINGUISHING TESTS

In AISSCE, questions of distinguishing tests are compulsorily asked and it awards you at least 2 marks.

There is limited number of distinguishing tests in Class XII Chemistry which can be easily learn and secure marks.

Name of the Test	For which compound	What Happen	Reaction	Examples
Iodoform Test	This test is performed by the compound having Methyl Ketone (CH₃CO-) or CH₃CH(OH)-.	In the reaction yellow ppt of Iodoform (CHI₃) is produced.		1. Ethanal 2. Propanone 3. Butan-2-one 4. Ethanol 5. Propan-2-ol Etc.
FeCl₃ Test	This test is performed by Phenol.	Phenol gives violet colouration with FeCl₃ solution.		Phenol
NaHCO₃ Test (Sodium Bicarbonate Test)	This test is performed by Carboxylic acids (R/Ar-COOH)	Acid produces brisk effervescence with NaHCO₃.		All Carboxylic acids such as Ethanoic acid, Benzoic acid etc
Tollen’s Test (Silver Mirror Test)	This test is performed by Aldehydes (Aliphatic/Aromatic)	Aldehydes form Silver Mirror on the inner side of test tube when heated with Tollen’s reagent (Ammoniacal Silver Nitrate)		All Aldehydes such as Methanal, Ethanal, Benzaldehyde etc.
Fehling’s Test	This test is performed by Aliphatic Aldehydes.	Aliphatic aldehydes gives reddish brown precipate of cuprous oxide when warmed with a few drops of Fehling’s solution.		All Aliphatic aldehydes such as methanol, Ethanal, Propanal etc.
2,4-DNP Test (2, 4 – Dinitrophenyl hydrazine test)	This test is performed by the compounds having carbonyl group ( >C=O)	Aldehydes and ketones form yellow or orange precipitate of 2, 4 – dinitrophenyl hydrazone when they react with 2, 4 – dinitrophenyl hydrazine.		All aldehydes and ketones.
Litmus Test	This test is performed by carboxylic acids and phenols.	All carboxylic acids and phenols turn blue litmus red.		All carbylic acids such as Methanoic acid, Acetic acid, benzoic acid etc and phenol.
HgCl₂	This test is performed by Formic acid. It is used to distinguish between Formic other acids.	Formic acid reduces HgCl₂ to give white precipitate of Hg₂Cl₂.		Methanoic Acid (Formic Acid)
Hinsberg’s Test	This test is performed by amines and used to distinguish between 1°, 2° and 3° amines.	On treating amines with hinsberg’s reagent (benzene sulphonyl chloride) 1° amines gives N- alkyl benzene sulphonamide which is soluble in alkali (aq. KOH). 2° amines gives N, N- dialkyl benzene sulphonamide which is insoluble in alkali (aq. KOH). 3° amines dosen’t react at all.		1°, 2° and 3° amines.
Carbylamine Test (Isocyanide Test)	This test is performed by 1° amines (Aliphatic as well as Aromatic). It is used to distinguish between primary amines secondary/ tertiary amines	Primary Amines react with chloroform in presence of alcoholic KOH to form foul smelling carbylamines.		All primary aliphatic amines and aromatic amine such as Ethanamine, Aniline etc.
Azo dye Test	This test is performed by 1° Aromatic amines. It is used to distinguish between 1° Aromatic amines and 1° Aliphatic amines.	1° Aromatic amines gives Brilliant Yellow. Orange or Red coloured dye on treating with HNO₂ followed by alkaline solution of 2-naphthol. 1° Aliphatic amines gives brisk effervescence of N₂ gas under these conditions.		Aniline forms Orange dye. Ethylamine gives N₂ gas and primary alcohols.