CBSE Class 12 chemistry practical, Organic qualitative analysis · Organic qualitative analysis

Source: CBSE Class 12 chemistry practical syllabus · use your school laboratory manual (NCERT Lab Manual where your school uses it).

Detection of functional groups (Class 12) (Class 12 chemistry practical)

You work through the Class 12 organic test scheme on known or unknown samples.

Record only observations you actually see — the manual’s table is your authority for reagents.

Published practice page. Concentrations, masses, and numerical answers come from your school laboratory manual and your own readings — not invented here. Not yet reviewed by a named chemistry reviewer. Version 1.0.0, updated 2026-10-03.

Safety — read before you start

Safety warning. Practise here. Perform the real experiment only in your school lab, with your teacher present.

Bromine in CCl₄ causes severe burns and CCl₄ is toxic — teacher protocol only.
Sodium metal reacts violently with water — teacher must supervise any Na test.
Tollens reagent can form explosive residues if stored — use freshly and dispose as directed.
Acids, alkalis, and Fehling’s / 2,4-DNP reagents are corrosive or harmful — gloves and goggles.

Wear: Lab coat, Splash goggles, Gloves, as your teacher directs.

Follow your teacher’s disposal instructions. Do not pour leftovers down a household drain.

Loads only after you tap. Use the lab hands to pick up and use equipment (pointer hidden in the scene). Falls back to a flat diagram if WebGL is unavailable.

Aim

To identify functional groups present in the organic compound(s) issued in your laboratory manual using the prescribed qualitative tests.

Methods and quantities can differ between schools. Follow your teacher's instructions.

Apparatus and chemicals

Apparatus and chemicals
Item	Note
Test tubes and rack	Clean and dry.
Water bath	For Fehling’s, iodoform, etc., if manual requires heat.
Droppers	One per reagent where possible.
Organic sample(s) (sample)	School-issued only.
Test reagent set (reagents)	May include: Br₂/CCl₄, Baeyer, Na metal, ceric ammonium nitrate, neutral FeCl₃, 2,4-DNP, Tollens, Fehling, NaHCO₃, Hinsberg, nitrous acid test for aromatic amines — follow manual list.

Test tubes and reagent bottle for organic tests — Each functional-group test has its own reagent and colour change. Match reagents only to your laboratory manual.

Theory and reaction

Open

Unsaturation: decolourisation of bromine in CCl₄ or cold dilute alkaline KMnO₄ (Baeyer).

Alcohols: ceric ammonium nitrate (yellow to red for some alcohols) or Lucas test if manual lists it.

Phenols: violet/blue/green with neutral FeCl₃; dissolve in NaOH.

Aldehydes vs ketones: Tollens’ mirror or Fehling’s reduction (aldehydes typically positive under conditions taught).

Carboxylic acids: NaHCO₃ effervescence (CO₂). Amines: reaction with nitrous acid (primary aromatic → diazonium chemistry as taught).

Tollens reagent oxidises aldehydes to carboxylate and deposits silver mirror.

Procedure

Note physical state, colour, and odour only as teacher permits.
Test solubility in water and litmus if manual starts there.
Run unsaturation tests if hydrocarbon character is possible.
Perform alcohol/phenol, aldehyde/ketone, acid, and amine tests in the manual’s order. Record each observation.Safety: Many reagents are flammable or corrosive. Tollens must be fresh; do not store explosive silver fulminates.
Summarise which functional groups are confirmed by at least one positive and matching negative controls.

Observation table

Enter the readings from your school lab in the practical file below. This page does not fill them in for you.

Type the readings in your practical file

S. No.	Test (—)	Observation (—)	Functional group inference (—)
1
2
3

Calculation

Qualitative only — no titre.

Result

State the functional group(s) present with supporting tests.

Precautions

Small quantities — qualitative tests need drops, not grams.
Never pipette organics by mouth.
Dispose of Tollens waste as teacher directs.

Viva questions

Answer one question at a time. The full answers stay closed until you open them.

Question 1 of 4

Tollens’ test is positive for typical…

A. AldehydesB. Ketones generallyC. Saturated hydrocarbonsD. NaCl

Pick an answer first.

Show all questions and answers

Tollens’ test is positive for typical…
Answer: Aldehydes. Reason: Aldehydes reduce Tollens; simple ketones usually do not.
NaHCO₃ effervescence strongly suggests…
Answer: Carboxylic acid. Reason: Acids release CO₂ with bicarbonate.
2,4-DNP test gives…
Answer: Yellow/orange precipitate with carbonyl compounds. Reason: 2,4-dinitrophenylhydrazine precipitates with aldehydes and ketones.
Baeyer’s reagent tests for…
Answer: Unsaturation (C=C / C≡C under taught conditions). Reason: Cold dilute alkaline KMnO₄ decolourises with many unsaturated compounds.

Common mistakes

Calling every FeCl₃ colour ‘phenol’ without manual colour key.
Positive iodoform assumed for all alcohols (only specific structures).
Using ketone-positive Tollens (should be negative for simple ketones).

Frequently asked questions

Can I do this at home?: No. Use this page to practise the order of steps and viva. Do the real experiment only in your school laboratory, with your teacher present.

Your practical file

Name, school, and roll number are optional and are not sent anywhere.

The practical file opens on this device.

Review

Not yet reviewed by a named chemistry reviewer. Published for practice only — follow your teacher and laboratory manual for quantities and safety.

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Related note

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