Q.70 Chemistry · Section A ⭐ 360° Option Elimination Active

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NEET 2024 Chemistry Question 70 Solution

Topic: Some Basic Concepts of Chemistry · Official NTA Booklet Code T1

Question

The highest number of helium atoms is in

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Verified Against NTA Final Answer Key

Option (3) : 4 mol of helium

📚 Some Basic Concepts of Chemistry Easy

📋 Given Parameters & Problem Setup

Option 1 4 g of helium

Option 2 2.271098 L of helium at STP

Option 3 4 mol of helium

Option 4 4 u of helium

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The 30-Second Exam Hall Shortcut: ⚡ Mole vs Gram vs u Magnitude Hack

⏱️ Save ~30 seconds

4 mol = 4 × N_A ≈ 2.4 × 10²⁴ atoms! 4 g is only 1 mol (N_A), 2.27 L is 0.1 mol, and 4 u is literally ONE SINGLE ATOM!

1 4 mol of helium contains 4 × N_A = 4 × (6.022 × 10²³) ≈ 2.41 × 10²⁴ atoms.

2 4 g of helium: moles = mass / molar mass = 4 g / 4 g/mol = 1 mol = 1 N_A atoms.

3 2.271098 L at STP (1 bar, 273.15 K): moles = 2.271098 / 22.71098 = 0.1 mol = 0.1 N_A atoms.

4 4 u of helium: 1 atom of He has mass 4 u, so 4 u contains exactly 1 atom!

5 Clearly, 4 mol contains by far the highest number of atoms -> Option (3) in 3 seconds!

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Why You Can 100% Trust This Shortcut: NCERT Chemistry · Some Basic Concepts of Chemistry (Mole concept, Avogadro constant, and atomic mass unit definitions).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluating Option (1): 4 g of Helium

Molar mass of helium is 4.00 g/mol. Calculating moles and number of atoms:

n = \frac{4\;\text{g}}{4\;\text{g/mol}} = 1\;\text{mol} \implies N = 1 \times N_A = 6.022 \times 10^{23}\;\text{atoms}

Step 2

Evaluating Option (2): 2.271098 L of Helium at STP

At standard temperature and pressure (T = 273.15 K, P = 1 bar), the molar volume of an ideal gas is 22.71098 L/mol:

n = \frac{2.271098\;\text{L}}{22.71098\;\text{L/mol}} = 0.1\;\text{mol} \implies N = 0.1 \times N_A = 6.022 \times 10^{22}\;\text{atoms}

Step 3

Evaluating Option (3): 4 mol of Helium

By definition of the mole, 1 mole contains Avogadro’s number of entities:

N = 4 \times N_A = 4 \times (6.022 \times 10^{23}) = 2.4088 \times 10^{24}\;\text{atoms}

Step 4

Evaluating Option (4): 4 u of Helium

The unified atomic mass unit u is the mass of a single nucleon scale. Because one helium-4 atom has a mass of 4.00 u:

N = \frac{4\;\text{u}}{4\;\text{u/atom}} = 1\;\text{atom}

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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:

Contains 1 N_A atoms, which is 4 times fewer than 4 mol.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing 4 grams with 4 moles.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Contains only 0.1 N_A atoms.

⚠️

Student Fallacy (Why candidates pick this trap): Being intimidated by the long decimal number.

3 (3)

✓ 100% Correct

Verdict & Scientific Reason:

Contains 4 N_A ≈ 2.41 × 10²⁴ atoms, the highest quantity.

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Why this is airtight: None.

4 (4)

✗ Incorrect

Verdict & Scientific Reason:

Contains exactly ONE single atom.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing unified atomic mass unit (u) with grams or moles.

⚠️

NTA Trap Alert: Equating 4 u with 4 grams or 4 moles

4 u is microscopically 1 single atom (6.64 × 10⁻²⁴ g). 4 g is 1 mole (6.02 × 10²³ atoms). 4 mol is 4 moles (2.41 × 10²⁴ atoms).

🛡️ How to avoid the -1 mark: Remember: "u" is for single atoms; "g" is for moles of atoms; "mol" multiplies by 6.022 × 10²³.

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Core NEET Syllabus Standard

Chemistry Core Physical Chemistry · Some Basic Concepts of Chemistry Standard Benchmark

Core Scientific Principle Tested:

"Number of particles = moles × Avogadro constant; 4 mol has 4 NA particles, exceeding 4 g (1 NA) and 4 u (1 particle)."

Syllabus Focus: Mole Concept, Atomic Mass Unit, and Molar Volume

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Moles are mountains, grams are hills, and u is just a grain that chills!

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NEET 2024 Chemistry Question 70 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Mole vs Gram vs u Magnitude Hack

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluating Option (1): 4 g of Helium

Evaluating Option (2): 2.271098 L of Helium at STP

Evaluating Option (3): 4 mol of Helium

Evaluating Option (4): 4 u of Helium

360° Option Elimination Engine Key Feature

NTA Trap Alert: Equating 4 u with 4 grams or 4 moles

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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