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NEET CHEMISTRYSome Basic Concepts of ChemistryMedium

Question

The maximum number of molecules is present in:

A

5L of N₂ gas at STP

B

0.5 g of H₂ gas

C

10g of O₂ gas

D

15 L of H₂ gas at STP

Step-by-Step Solution

  1. Identify the Principle: The number of molecules is directly proportional to the number of moles (nn).
  • For gases at STP (Standard Temperature and Pressure), n=Volume (L)22.4n = \frac{\text{Volume (L)}}{22.4}.
  • For mass, n=Mass (g)Molar Mass (g/mol)n = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}}.
  1. Calculate Moles for each option:
  • Option 1: 5 L5\text{ L} of N2N_2 at STP. n=522.40.223 moln = \frac{5}{22.4} \approx 0.223 \text{ mol}
  • Option 2: 0.5 g0.5\text{ g} of H2H_2. Molar mass of H2=2 g/molH_2 = 2\text{ g/mol}. n=0.52=0.25 moln = \frac{0.5}{2} = 0.25 \text{ mol}
  • Option 3: 10 g10\text{ g} of O2O_2. Molar mass of O2=32 g/molO_2 = 32\text{ g/mol}. n=1032=0.3125 moln = \frac{10}{32} = 0.3125 \text{ mol}
  • Option 4: 15 L15\text{ L} of H2H_2 at STP. n=1522.40.67 moln = \frac{15}{22.4} \approx 0.67 \text{ mol}
  1. Conclusion: Option 4 has the highest number of moles (0.670.67), therefore it contains the maximum number of molecules.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Some Basic Concepts of Chemistry. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYSome Basic Concepts of Chemistrymaximumnumbermoleculespresent

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