Q.93 Chemistry ⭐ 360° Option Elimination Active

NEET 2020 Chemistry Question 93 Solution

Topic: The p-Block Elements (Group 14) · Official NTA Booklet Code E1

Question

Identify the correct statements from the following: (a) CO2(g) is used as refrigerant for ice-cream and frozen food. (b) The structure of C60 contains twelve six carbon rings and twenty five carbon rings. (c) ZSM-5, a type of zeolite, is used to convert alcohols into gasoline. (d) CO is colorless and odourless gas.

(1)(a), (b) and (c) only
(2)(a) and (c) only
(3)(b) and (c) only
(4)(c) and (d) only

✓

Verified Against NTA Final Answer Key

Option (4) : (c) and (d) only

📚 The p-Block Elements (Group 14) Medium

📋 Given Parameters & Problem Setup

Statement (a) CO2(g) is used as refrigerant for ice-cream and frozen food

Statement (b) Structure of C60 contains 12 six-carbon rings and 20 five-carbon rings

Statement (c) ZSM-5, a type of zeolite, is used to convert alcohols into gasoline

Statement (d) CO is colorless and odourless gas

Question Objective Identify which statements are factually CORRECT

⚡

The 30-Second Exam Hall Shortcut: ⚡ "Dry Ice (SOLID CO2) is Refrigerant; C60 has 20 Six-Rings & 12 Five-Rings! (c) & (d) are True!"

⏱️ 30 seconds

Statement (a) is false because SOLID CO2 (dry ice), not gaseous CO2(g), is used as a refrigerant. Statement (b) is false because C60 contains TWENTY six-membered rings and TWELVE five-membered rings (the numbers are reversed!). Statements (c) and (d) are textbook true. Thus, (c) and (d) only (Option 4)!

1 Check (a): SOLID CO2 (dry ice) is the refrigerant, not CO2(g) -> (a) is FALSE.

2 Check (b): C60 fullerene has 20 six-membered rings and 12 five-membered rings -> (b) is FALSE (swapped!).

3 Check (c): ZSM-5 zeolite converts alcohols directly into gasoline -> (c) is TRUE.

4 Check (d): Carbon monoxide is a neutral, colorless, and odourless gas -> (d) is TRUE.

5 Correct statements: (c) and (d) only -> Option 4.

🛡️

Why You Can 100% Trust This Shortcut: NCERT Chemistry · The p-Block Elements (Group 14: Oxides of Carbon & Fullerenes)

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluate Statement (a): Refrigerant Use of CO2

SOLID carbon dioxide (dry ice) sublimes directly at $-78.5^\circ\text{C}$ without melting into liquid, making it ideal as a refrigerant for ice cream and frozen food. Statement (a) specifically claims " $\text{CO}_2\text{(g)}$ " (gaseous carbon dioxide) is used as the refrigerant, which is technically incorrect.

Step 2

Evaluate Statement (b): Ring Topology of Buckminsterfullerene C60

Buckminsterfullerene ( $C_{60}$ ) has a soccer-ball shape containing 60 carbon vertices. It consists of exactly TWENTY 6-membered hexagonal rings and TWELVE 5-membered pentagonal rings. Statement (b) deliberately inverts these numbers ("twelve six-carbon rings and twenty five-carbon rings"), making it blatantly false.

Step 3

Evaluate Statement (c): Shape-Selective Catalysis by ZSM-5

ZSM-5 (Zeolite Socony Mobil-5) is a microporous aluminosilicate shape-selective catalyst used in the petroleum industry to dehydrate alcohols directly into synthetic gasoline/petrol hydrocarbons ( $\text{Alcohols} \xrightarrow{\text{ZSM-5}} \text{Gasoline}$ ). This statement is completely accurate.

Step 4

Evaluate Statement (d): Physical Properties of CO

Carbon monoxide ( $\text{CO}$ ) is a colorless, odorless, and virtually water-insoluble toxic gas formed by incomplete combustion of carbon. This statement is factually true.

Step 5

Synthesize True Statements

Only statements (c) and (d) are correct, corresponding to Option 4.

⭐

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

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; statements (a) and (b) are both factually false.

⚠️

Student Fallacy (Why candidates pick this trap): Failing to catch that solid CO2 is needed for refrigerant and ring numbers in C60 are reversed.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; statement (a) states CO2(g) rather than dry ice (solid CO2).

⚠️

Student Fallacy (Why candidates pick this trap): Overlooking the physical state "(g)" in CO2(g).

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; statement (b) has the pentagon and hexagon counts inverted.

⚠️

Student Fallacy (Why candidates pick this trap): Flipping 20 hexagons and 12 pentagons in C60 fullerene.

4 D

✓ 100% Correct

Verdict & Scientific Reason:

Factually exact; ZSM-5 converts alcohols to gasoline, and CO is a colorless and odorless gas.

💡

Why this is airtight: None; rigorous precision across inorganic chemistry concepts.

⚠️

NTA Trap Alert: Fullerene C60 Ring Numbers & Dry Ice Physical State

C60 has: 20 HEXAGONS (6-membered) and 12 PENTAGONS (5-membered). Dry ice = SOLID CO2, not CO2 gas!

🛡️ How to avoid the -1 mark: Mnemonic: "20 Sixes, 12 Fives" (Hexagons are always more numerous in fullerenes!).

📖

Core NEET Syllabus Standard

Chemistry · The p-Block Elements Standard Benchmark

Core Scientific Principle Tested:

Syllabus Focus: Allotropes and Compounds of Carbon: Dry Ice, Fullerenes, Zeolites & Carbon Monoxide

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2020 Chemistry Question 93 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ "Dry Ice (SOLID CO2) is Refrigerant; C60 has 20 Six-Rings & 12 Five-Rings! (c) & (d) are True!"

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluate Statement (a): Refrigerant Use of CO2

Evaluate Statement (b): Ring Topology of Buckminsterfullerene C60

Evaluate Statement (c): Shape-Selective Catalysis by ZSM-5

Evaluate Statement (d): Physical Properties of CO

Synthesize True Statements

360° Option Elimination Engine Key Feature

NTA Trap Alert: Fullerene C60 Ring Numbers & Dry Ice Physical State

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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