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Purification And Characterisation Of Organic Compounds Important Questions for NEET Chemistry - 2026

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Practice Purification And Characterisation Of Organic Compounds Important Questions - Free PDF Download

If you are preparing for NEET Chemistry, the chapter Purification And Characterisation Of Organic Compounds is very important. Here, you will find NEET Important Questions with Answers selected by experts at Vedantu. This helps you focus on questions that really matter for the exam.


This chapter explains methods for purification like crystallization, sublimation, distillation, and chromatography, along with their principles and uses. You also study how to detect elements such as nitrogen, sulphur, phosphorus, and halogens. The basics of quantitative analysis, including estimation of carbon and hydrogen, and calculations of empirical and molecular formulae, are also included.


Practicing these questions makes tough concepts clearer and improves your exam readiness. Download the free NEET Important Questions PDF from Vedantu and start practicing today. Get ready for NEET Chemistry with the best handpicked questions and answers.


Practice Purification And Characterisation Of Organic Compounds Important Questions - Free PDF Download

1. Multiple choice questions.


Q1. Which method is most suitable for separating a mixture of naphthalene and common salt?


  • (a) Distillation
  • (b) Sublimation
  • (c) Crystallization
  • (d) Chromatography

Answer: (b) Sublimation.


Q2. In Lassaigne’s test for nitrogen, the blue color is obtained due to the formation of:


  • (a) Prussian blue
  • (b) Berlin green
  • (c) Ferric chloride
  • (d) Sodium nitroprusside

Answer: (a) Prussian blue.


Q3. The method used for the separation of butter from curd is:


  • (a) Distillation
  • (b) Filtration
  • (c) Centrifugation
  • (d) Sublimation

Answer: (c) Centrifugation.


Q4. The element detected by the white precipitate of AgCl in organic analysis is:


  • (a) Sulphur
  • (b) Nitrogen
  • (c) Phosphorus
  • (d) Chlorine

Answer: (d) Chlorine.


Q5. Which physical property is used for purification by distillation?


  • (a) Melting point
  • (b) Boiling point
  • (c) Solubility
  • (d) Density

Answer: (b) Boiling point.


2. Very Short Answer (VSA).


Q1. Define crystallization as used in organic compound purification.


Answer: Crystallization is a purification technique where an impure compound is dissolved in a suitable solvent and then allowed to form pure crystals upon slow cooling.


Q2. What is the Lassaigne’s test?


Answer: Lassaigne’s test is used to detect nitrogen, sulphur, and halogens in an organic compound by converting them into water-soluble ionic forms.


Q3. State the principle of chromatography.


Answer: Chromatography separates components based on differential partitioning between stationary and mobile phases due to differences in their adsorption or solubility.


Q4. How is sulphur detected qualitatively in organic compounds?


Answer: Sulphur is detected by the formation of a black precipitate of lead sulphide on adding lead acetate to the sodium extract.


Q5. Name a quantitative method for the estimation of nitrogen in an organic compound.


Answer: The Kjeldahl method is a common quantitative method used for estimating nitrogen content in organic compounds.


3. Short Answer Questions.


Q1. Explain how differential extraction is used to separate organic compounds.


Answer: Differential extraction is used to separate compounds based on their different solubilities in immiscible solvents. The mixture is shaken with a specific solvent in a separatory funnel. The desired compound separates into the solvent where it is most soluble, while impurities remain in the other layer. This process can be repeated for purity.


Q2. Describe the steps in the quantitative estimation of carbon and hydrogen in an organic compound.


Answer: The estimation involves oxidizing the compound in the presence of copper oxide. Carbon converts to $CO_2$ and hydrogen to $H_2O$. Both are absorbed in suitable absorbents and weighed. The increase in mass gives the amounts of carbon and hydrogen present in the sample.


Q3. Calculate the empirical formula of a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass.


Answer:

  1. Divide each percent by atomic masses: C: $\frac{40}{12}=3.33$; H: $\frac{6.7}{1}=6.7$; O: $\frac{53.3}{16}=3.33$.
  2. Divide all by smallest ratio: C : H : O = 1 : 2 : 1.
  3. Empirical formula is $CH_2O$.

Q4. How is chromatography useful in organic compound purification?


Answer: Chromatography separates organic mixtures based on differential adsorption or solubility on a stationary phase and a moving solvent phase. It helps obtain pure components from complex mixtures and is especially effective when only small differences exist in a compound's properties.


Q5. Why is it necessary to use a solvent in which the solute has appreciable solubility at high temperatures but very low at low temperatures during crystallization?


Answer: This ensures that the solute dissolves completely at high temperatures but crystallizes out on cooling. It allows efficient precipitation of pure crystals while leaving impurities in the solution.


4. True or False Questions.


Q1. Distillation can be used to separate a mixture of two liquids with widely different boiling points.


Answer: True.


Q2. Nitrogen cannot be detected by Lassaigne’s test if the compound does not contain hydrogen.


Answer: True.


Q3. Sublimation is useful only for separating volatile solids from non-volatile impurities.


Answer: True.


Q4. The empirical formula always represents the actual number of atoms in a molecule.


Answer: False.


Q5. Silver nitrate is used to detect halogens in organic compounds.


Answer: True.


3. Fill in the Blanks Questions.


Q1. In the estimation of nitrogen using Kjeldahl’s method, the ammonia evolved is absorbed in _________.


Answer: standard acid solution


Q2. The white precipitate formed on adding silver nitrate to sodium extract confirms the presence of ________ in an organic compound.


Answer: chlorine


Q3. Separation of a coloured mixture into its pure components is best achieved by ________.


Answer: chromatography


Q4. Phosphorus is detected in organic compounds by forming a yellow precipitate of ________.


Answer: ammonium phosphomolybdate


Q5. The molecular formula is always a simple whole-number multiple of the ________ formula.


Answer: empirical


Why Learning Purification and Characterisation of Organic Compounds Matters for NEET Chemistry

Understanding purification and characterisation helps NEET aspirants answer practical as well as theory questions in Chemistry. Practicing these topics builds a strong base in organic analysis and develops your skills for both board and competitive exams like NEET.


Learning chromatography, distillation, and other techniques allows students to solve application-based questions and perform accurate calculations. These methods are often repeated in NEET Chemistry, increasing your confidence in each organic section and making revision easier every year.


Topics like Lassaigne’s test, empirical formula, and quantitative analysis appear in various NEET questions. With focused practice from Vedantu’s materials, you’ll approach these common areas using the best strategies and gain clarity for Chemistry concepts that carry high exam weightage.


FAQs on Purification And Characterisation Of Organic Compounds Important Questions for NEET Chemistry - 2026

1. What are the most important question types asked from Purification and Characterisation of Organic Compounds in NEET?

NEET often asks MCQs, assertion-reason pairs, and numericals from this chapter. Focus on the principles of purification methods, identification of techniques, and basic calculations for empirical and molecular formulae. Some exam-focused questions may directly test detection of elements or steps in chromatographic separation.

2. Which purification techniques should I focus on for chapter-wise practice and NEET questions?

Pay close attention to crystallization, sublimation, distillation, differential extraction, and chromatography. These methods often appear as statement-based or MCQ questions. Know the basic principles, suitable examples, and specific uses of each technique for quick identification in the exam.

3. How do NEET questions typically test qualitative analysis of nitrogen, sulphur, phosphorus, and halogens?

NEET can ask about detection procedures and test reagents for each element. Be prepared for questions like:

  • Which test confirms nitrogen in an organic compound?
  • Name the reagent for halogen detection.
  • What colour change indicates sulphur presence?

4. What exam-focused numericals are common from quantitative analysis in this chapter?

Students often encounter numerical problems on estimation of carbon, hydrogen, and nitrogen. Expected question patterns include:

  1. Given data from combustion or Kjeldahl method, calculate percentage composition.
  2. Solve for empirical or molecular formula from mass percentages.

5. How should students approach assertion reason and MCQs from Purification and Characterisation for NEET?

Read both statements carefully in assertion reason questions. MCQs may ask for correct technique identification or principle application. Use elimination to rule out incorrect statements. Always link each question to the core concept; don't just memorize—understand the logic behind every process.

6. What are common mistakes to avoid while solving important questions from this chapter?

Students often mix up purification techniques and qualitative analysis steps. Always verify reagents, remember which technique matches which compound, and avoid careless calculation errors in numericals. Double-check units and final answers, especially in empirical formulae questions.

7. Which revision strategy helps for NEET chapter-wise practice of this topic?

For effective revision:

  • Practice previous years’ NEET questions and expected numericals.
  • Create summary notes for detection tests and purification steps.
  • Attempt mixed MCQs: principles, methods, interpretations.
Regular, focused practice improves accuracy and recall under exam pressure.