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Class 11 chemistry · linked to Hydrocarbons · Organic qualitative analysis

Source: CBSE Class 11 chemistry practical syllabus · use your school laboratory manual (NCERT Lab Manual where your school uses it).

Tests for unsaturation (Class 11 chemistry practical)

You check whether a sample decolourises bromine water/CCl₄ solution or alkaline KMnO₄.

Saturated alkanes typically do not; alkenes/alkynes do under the conditions your manual describes.

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 causes severe burns and respiratory harm.
  • CCl₄ and many organics are toxic — teacher protocol only.
  • KMnO₄ stains and is an oxidiser.

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 test the given organic sample(s) for unsaturation using the reagent(s) prescribed in your laboratory manual.

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

Apparatus and chemicals

Apparatus and chemicals
ItemNote
Test tubesDry if the manual uses CCl₄.
DroppersSeparate for each reagent.
Hydrocarbon / organic sample (sample)May be liquid or solution as issued.
Bromine reagent (Br2)Use the strength and solvent in your laboratory manual.
Baeyer’s reagent (KMnO4)Cold dilute alkaline KMnO₄ as your manual defines.

Theory and reaction

Open

Alkenes add Br2 across the double bond → brown/orange bromine colour fades.

Alkaline KMnO4 oxidises alkenes; purple fades and brown MnO2 may appear (Baeyer’s test).

Aromatic rings under these mild tests usually do not behave like alkenes — follow your syllabus wording.

Alkene plus bromine gives a vicinal dibromide; colour of bromine fades.

Picture guide

Test tube with orange bromine solution fading
Bromine (or Baeyer’s reagent) can decolourise when it adds to a double or triple bond. Confirm with the test your teacher sets.

Procedure

  1. Place the sample volume your manual states in a clean tube.
  2. Add bromine reagent dropwise. Note whether the colour persists or fades.Safety: Bromine is corrosive and toxic. Teacher-controlled reagent only.
  3. In a fresh tube, add cold Baeyer’s reagent as directed. Note purple fade / brown ppt.
  4. Conclude saturated vs unsaturated for the sample you were given.

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

Calculation

No titre. Qualitative only.

Result

State whether the sample tested unsaturated under your manual’s criteria.

Precautions

  • Work in a cupboard / good ventilation if your teacher requires it for Br₂.
  • Do not dump bromine residues in the sink.

Viva questions

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

Question 1 of 3

Baeyer’s reagent is essentially…

Answer choices

Pick an answer first.

Show all questions and answers

  1. Baeyer’s reagent is essentially…

    Answer: Cold dilute alkaline KMnO₄. Reason: Alkaline KMnO₄ used cold and dilute.

  2. Br₂ in CCl₄ fading with an alkene is mainly…

    Answer: Electrophilic addition. Reason: Addition across the π bond.

  3. General formula for open-chain alkenes is…

    Answer: CₙH₂ₙ. Reason: One double bond: CₙH₂ₙ.

Common mistakes

  • Calling every colour fade “alkene” when the sample was diluted wrongly.
  • Using hot concentrated KMnO₄ and reading it as Baeyer’s mild test.
  • Skipping the control tube with a known saturated compound when asked.

Frequently asked questions

Can I do this at home?
No. Use this page to practise the order of ideas and steps. 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 notes

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