Q.72 Chemistry ⭐ 360° Option Elimination Active

NEET 2025 Chemistry Question 72 Solution

Topic: Organic Chemistry - Some Basic Principles and Techniques · Official NTA Booklet Code 45

Question

Match List I (Mixture) with List II (Method of Separation). List I: A. CHCl₃ + C₆H₅NH₂; B. Crude oil in petroleum industry; C. Glycerol from spent-lye; D. Aniline - water. List II: I. Distillation under reduced pressure; II. Steam distillation; III. Fractional distillation; IV. Simple distillation. Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (1) : A-IV, B-III, C-I, D-II

📚 Organic Chemistry - Some Basic Principles and Techniques Easy

📋 Given Parameters & Problem Setup

Mixture A CHCl₃ + C₆H₅NH₂ (Chloroform + Aniline, large boiling point difference)

Mixture B Crude oil in petroleum industry (Multi-component mixture with close boiling points)

Mixture C Glycerol from spent-lye (High boiling liquid decomposing at normal bp)

Mixture D Aniline - water (Steam volatile substance immiscible with water)

⚡

The 30-Second Exam Hall Shortcut: ⚡ Purification Technique Fingerprint

⏱️ Save ~40 seconds

Large ΔT_b (CHCl₃ + Aniline) = Simple distillation (A-IV). Petroleum fractions = Fractional distillation (B-III). Glycerol (spent-lye, decomposes at bp) = Distillation under reduced pressure (C-I). Aniline-water (steam volatile) = Steam distillation (D-II)!

1 A. CHCl₃ (bp 334 K) and Aniline (bp 457 K) have a massive boiling point difference of ~123 K ⟹ Simple Distillation (A matches IV).

2 Look at options: Only Option (1) and (2) start with A-IV, B-III.

3 B. Crude oil has multiple hydrocarbon fractions boiling closely ⟹ Fractional Distillation (B matches III).

4 C. Glycerol boils at 563 K but decomposes before reaching this temperature; it is recovered from spent-lye by ⟹ Distillation under reduced pressure (C matches I).

5 D. Aniline is steam volatile and immiscible with water ⟹ Steam Distillation (D matches II).

6 Complete match: A-IV, B-III, C-I, D-II.

7 Select Option (1) in under 10 seconds!

🛡️

Why You Can 100% Trust This Shortcut: Chromatographic and Fractional Distillation Principles (NCERT Chemistry · Organic Chemistry: Some Basic Principles and Techniques).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Match Simple Distillation and Fractional Distillation

Examine separation methods based on boiling point differentials:

\text{Simple Distillation (IV): } \Delta T_b > 30-50\text{ K} \implies \text{CHCl}_3\,(334\text{ K}) + \text{C}_6\text{H}_5\text{NH}_2\,(457\text{ K})

• A matches IV (A-IV).
• Fractional Distillation (III): Used when boiling point differences are small (fractions of crude oil in petroleum refining).
• B matches III (B-III).

Step 2

Match Vacuum Distillation (Reduced Pressure) and Steam Distillation

Examine specialized distillation techniques for delicate or steam-volatile compounds:

\text{Distillation under reduced pressure (I): Used for liquids decomposing at or below normal bp}

• Glycerol boils at 563 K with decomposition, but boils at 453 K without decomposition under 12 mm Hg pressure; it is separated from spent-lye by vacuum distillation (C-I).
• Steam Distillation (II): Used for substances which are steam volatile and immiscible with water (such as the aniline-water mixture, D-II).

Step 3

Synthesize the Complete Match

Assemble all pairs:

\text{A-IV, B-III, C-I, D-II} \implies \text{Option (1)}

• Matches Option (1) with 100% textbook precision.

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Chloroform+aniline (simple), crude oil (fractional), glycerol (reduced pressure), aniline+water (steam).

💡

Why this is airtight: None; textbook purification methods.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Swaps glycerol (reduced pressure) with aniline-water (steam distillation).

⚠️

Student Fallacy (Why candidates pick this trap): Confusing steam distillation with vacuum distillation.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Uses fractional distillation for chloroform+aniline.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking simple distillation is for petroleum.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Scrambled match.

⚠️

Student Fallacy (Why candidates pick this trap): Multiple errors.

⚠️

NTA Trap Alert: Glycerol Decomposition Trap

Glycerol from spent-lye is the single most famous NCERT example of "distillation under reduced pressure". Students who forget that glycerol decomposes at its normal boiling point mistakenly pick simple or steam distillation.

🛡️ How to avoid the -1 mark: Remember: Glycerol = Reduced Pressure (Vacuum); Aniline = Steam Distillation!

📖

Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Organic Chemistry - Some Basic Principles and Techniques Standard Benchmark

Core Scientific Principle Tested:

"Simple: large ΔT_b; Fractional: close boiling points; Reduced pressure: decomposes at bp; Steam: steam-volatile & water-immiscible."

Syllabus Focus: Purification of Organic Compounds: Distillation Methods

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

CHCl₃/Aniline = Simple (IV), Petroleum = Fractional (III), Glycerol = Vacuum (I), Aniline/Water = Steam (II)!

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NEET 2025 Chemistry Question 72 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Purification Technique Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Match Simple Distillation and Fractional Distillation

Match Vacuum Distillation (Reduced Pressure) and Steam Distillation

Synthesize the Complete Match

360° Option Elimination Engine Key Feature

NTA Trap Alert: Glycerol Decomposition Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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