Q.57 Chemistry · Section A ⭐ 360° Option Elimination Active

NEET 2024 Chemistry Question 57 Solution

Topic: Organic Chemistry - Some Basic Principles and Techniques · Official NTA Booklet Code T1

Question

On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

(1)Distillation
(2)Chromatography
(3)Crystallization
(4)Sublimation

✓

Verified Against NTA Final Answer Key

Option (4) : Sublimation

📚 Organic Chemistry - Some Basic Principles and Techniques Easy

📋 Given Parameters & Problem Setup

Phenomenon Direct phase transformation from solid to vapour on heating without passing through liquid state

Objective Purification technique for such solid substances

⚡

The 30-Second Exam Hall Shortcut: ⚡ Phase Change Direct Definition

⏱️ Save ~30 seconds

Solid to Gas without Liquid = Sublimation! Textbook purification technique for camphor, benzoic acid, naphthalene, iodine, and anthracene!

1 Direct transition from Solid -> Vapour on heating is the physical definition of sublimation.

2 Purification technique based on this principle is Sublimation.

3 Distillation separates liquids based on boiling point differences.

4 Chromatography separates based on differential adsorption/partition.

5 Crystallization relies on solubility differences in a suitable solvent.

6 Direct match: Option (4) in 2 seconds!

🛡️

Why You Can 100% Trust This Shortcut: NCERT Chemistry · Organic Chemistry - Some Basic Principles and Techniques (Purification of organic compounds: Sublimation).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Thermodynamic and Physical Basis of Sublimation

Sublimation is a phase transition that occurs at temperatures and pressures below a substance’s triple point in its phase diagram, where the solid phase’s vapour pressure equals atmospheric pressure before melting occurs. When heated, the solid transitions directly into vapour without entering the liquid state:

\text{Solid} \;\xrightleftharpoons[\text{deposition}]{\text{sublimation}}\; \text{Vapour}

Step 2

Application in Purification of Organic Solids

Sublimation is employed to separate sublimable solids (e.g., naphthalene, anthracene, benzoic acid, camphor, ammonium chloride, iodine) from non-sublimable impurities. On cooling, the pure vapours condense directly into solid form on a chilled surface (such as an inverted funnel plugged with cotton), leaving non-volatile impurities behind in the dish.

\text{Impure Solid} \xrightarrow{\Delta} \text{Pure Vapour} + \text{Residue (Insoluble Impurities)} \xrightarrow{\text{Cooling}} \text{Pure Crystal Condensate}

⭐

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 (1)

✗ Incorrect

Verdict & Scientific Reason:

Distillation is used to separate volatile liquids from non-volatile impurities or liquid mixtures with different boiling points.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing vaporization of liquids with sublimation of solids.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Chromatography is a separation technique based on differential partitioning between stationary and mobile phases.

⚠️

Student Fallacy (Why candidates pick this trap): Equating phase transition with chromatographic separation.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Crystallization is based on the differential solubility of a compound and its impurities in a chosen solvent.

⚠️

Student Fallacy (Why candidates pick this trap): Assuming crystal formation involves direct vapour-solid transition.

4 (4)

✓ 100% Correct

Verdict & Scientific Reason:

Verbatim physical and textbook definition of sublimation purification.

💡

Why this is airtight: None.

⚠️

NTA Trap Alert: Distillation vs Sublimation

Both involve vapor formation on heating, but distillation starts from a liquid, whereas sublimation starts directly from a solid.

🛡️ How to avoid the -1 mark: Check the starting phase: Solid directly to vapour without melting = Sublimation.

📖

Core NEET Syllabus Standard

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

Core Scientific Principle Tested:

"Sublimation is used to separate sublimable substances that pass directly from solid to vapour on heating from non-sublimable impurities."

Syllabus Focus: Methods of Purification of Organic Compounds

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Skip the liquid, leap the station: Solid to gas is Sublimation!

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NEET 2024 Chemistry Question 57 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Phase Change Direct Definition

Step-by-Step Rigorous Workflow & Mathematical Proof

Thermodynamic and Physical Basis of Sublimation

Application in Purification of Organic Solids

360° Option Elimination Engine Key Feature

NTA Trap Alert: Distillation vs Sublimation

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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