Chemistry · Class 11 · Purification and Characterisation of Organic Compounds

Purification and Characterisation of Organic Compounds for JEE

Everything you need for this topic on one page: the ideas, the formulas, the traps, and free lectures that explain it well.

Last updated: 26 October 2026

Direct answer

Crystallisation, distillation, sublimation, chromatography, detection of elements (Lassaigne's test) and quantitative estimation of C, H, N, S, halogens.

Key ideas

Purification and Characterisation of Organic Compounds: what you must understand

Steam distillation for steam-volatile, water-immiscible compounds
Lassaigne's test converts N, S, halogens to ionic forms
Rf value = distance by compound / distance by solvent
Kjeldahl method is not used for nitro, azo or ring nitrogen

Formula sheet

Must-know formulas for Purification and Characterisation of Organic Compounds

% C = (12/44) × (mass of CO₂ / mass of compound) × 100
% H = (2/18) × (mass of H₂O / mass) × 100
Kjeldahl: % N = 1.4 × N × V / mass
Carius: % X from mass of AgX

One-page formula sheet

Printable Purification and Characterisation of Organic Compounds formula sheet: formulas, key ideas and traps on one page. Save it as a PDF for offline revision.

Avoid

Common mistakes students make

Using Kjeldahl for nitrobenzene
Mixing up which method separates which mixture
Arithmetic errors in percentage composition

For the exam

How this topic is asked in JEE

Appears regularly; quick marks. Usually one direct question, often from NCERT examples.

Prerequisites: Mole Concept and Stoichiometry.

NCERT map

Where Purification and Characterisation of Organic Compounds is in NCERT

Chapter names follow the current rationalised NCERT textbooks. Read these sections before solving PYQs.

Class	Book	Chapter	Sections JEE asks from
Class 11	Chemistry Part II	Organic Chemistry: Some Basic Principles and Techniques	Purification of Organic Compounds; Qualitative Analysis of Organic Compounds; Quantitative Analysis

JEE Advanced level

A JEE Advanced-level example on Purification and Characterisation of Organic Compounds

Question. An organic compound contains only C, H, N and S. In Lassaigne's test, the sodium fusion extract gives a violet coloration with sodium nitroprusside and Prussian blue color with FeCl3 after adding FeSO4. On quantitative analysis: (i) 0.30 g of the compound on combustion gave 0.352 g of CO2 and 0.18 g of H2O, (ii) 0.30 g of the compound on Kjeldahl's method required 20 mL of 0.1 M H2SO4 for complete neutralization of evolved ammonia. If the molar mass of the compound is 75 g/mol, determine its molecular formula.

Show solution

Lassaigne's test confirms: violet color with sodium nitroprusside means S is present, Prussian blue with FeCl3 means N is present.
Mass of C = (12/44) × 0.352 = 0.096 g, so %C = (0.096/0.30) × 100 = 32%
Mass of H = (2/18) × 0.18 = 0.02 g, so %H = (0.02/0.30) × 100 = 6.67%
For N: moles of H2SO4 = 0.02 × 0.1 = 0.002 mol. Since H2SO4 + 2NH3 → (NH4)2SO4, moles of N = 0.004. Mass of N = 0.056 g, so %N = 18.67%
%S = 100 − 32 − 6.67 − 18.67 = 42.67%. Molar ratio C:H:N:S = (32/12):(6.67/1):(18.67/14):(42.67/32) = 2:5:1:1
Empirical formula = C2H5NS with mass 75, which equals molar mass. Molecular formula = C2H5NS (thioacetamide)

Answer: C₂H₅NS

This example was solved twice independently and both solutions agree.

Free lectures

Best free lectures for Purification and Characterisation of Organic Compounds

Full-chapter free lectures picked from YouTube search results by views, from established JEE channels (mostly in Hinglish). Use the subtopic list to jump straight to the part you need (timestamps come from each video's own chapter list). Watch one, then solve PYQs the same day.

PURIFICATION OF ORGANIC COMPOUNDS in 1 Shot - All Concepts, Tricks & PYQs Covered | JEE Main & Adv. — JEE Wallah, 4:06:54
Purification Technique, Qualitative & Quantitative Analysis + Optical Isomerism ONE SHOT🔥Nitin Sir — ALLEN JEE, 8:27:21
Jump to a subtopic (18)
- 00:00:00 Introduction
- 00:08:42 Polarimeter Experiment
- 00:30:21 Element of Symmetry
- 01:50:46 Chirality and Chiral Center
- 02:21:26 Interconversion of Various Projections
- 03:04:57 R/S | D/L | Configuration in Optical Isomers
- 03:31:23 Enantiomers & Diastereomers
- 04:12:21 Meso Compounds
- 04:15:30 Racemic Mixture & Enantiomeric Excess
- 04:20:41 Amine Inversion
- 04:23:29 Resolution
- 04:37:05 Calculation of Stereoisomers
- 05:25:41 Purification Techniques
- 05:35:00 All Distillation Techniques
- 06:00:41 Solvent Extraction
- 06:27:11 Chromatography
- 07:23:20 Qualitative Analysis of Organic Compounds
- 07:43:26 Quantitative Analysis of Organic Compounds

Practise

Where to practise for free

1 JEE Main 2026 PYQs on Purification and Characterisation of Organic Compounds, with solutions.
Read the chapter in NCERT textbooks (official, free), then solve its NCERT Exemplar (official, free) questions.
Chapter-wise past questions: JEE Main and Advanced PYQs and question bank.
Timed practice tests: NTA Abhyas practice tests (official, free) and our free mock tests.
See it move: interactive simulation.

FAQs

Frequently asked questions

Is Purification and Characterisation of Organic Compounds important for JEE Main 2027?

Appears regularly; quick marks. It is part of the official 'Purification and Characterisation of Organic Compounds' unit in the JEE Main 2027 syllabus.

What are the most important formulas in Purification and Characterisation of Organic Compounds?

% C = (12/44) × (mass of CO₂ / mass of compound) × 100; % H = (2/18) × (mass of H₂O / mass) × 100; Kjeldahl: % N = 1.4 × N × V / mass.

How should I study Purification and Characterisation of Organic Compounds for JEE?

Understand the key ideas from NCERT or one full lecture, learn the formula sheet, then solve 25–30 past JEE questions on the topic. Usually one direct question, often from NCERT examples.