Class 11 Chemistry Chapter 1: Some Basic Concepts of Chemistry (Mole Concept) – Part 1 | Chemistry Achievers Academy

 

Class 11 Chemistry Chapter 1: Some Basic Concepts of Chemistry (Mole Concept) – Important Topics, NEET Weightage & Chapter Introduction | Chemistry Achievers Academy

Class 11 Chemistry Chapter 1 Mole Concept MCQs | NEET & JEE Chemistry | Chemistry Achievers Academy

Master Class 11 Chemistry Chapter 1 – Some Basic Concepts of Chemistry (Mole Concept). Learn the important topics, NEET/JEE weightage, frequently asked concepts, chapter-wise MCQs, PYQs, formula sheet, and revision notes.

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📚 Chapter 1: Some Basic Concepts of Chemistry (Mole Concept)

📖 Chapter Introduction

Chemistry is often called the Central Science because it connects Physics, Biology, Environmental Science, and Medicine. The first chapter, Some Basic Concepts of Chemistry, forms the foundation for almost every other chapter in Class 11 and Class 12 Chemistry.

This chapter introduces the language of chemistry through concepts such as the mole, Avogadro constant, molar mass, empirical and molecular formulae, stoichiometry, and chemical calculations. These topics are essential for solving numerical problems in NEET, JEE Main, JEE Advanced, CUET, CBSE Board Exams, and other competitive examinations.

Students who master this chapter will find it much easier to understand later topics such as Atomic Structure, Chemical Bonding, Thermodynamics, Equilibrium, Electrochemistry, and Organic Chemistry.

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🎯 Important Topics & Frequently Asked Questions from This Chapter

The following concepts are repeatedly tested in NEET, JEE Main, JEE Advanced, and CBSE Board examinations:

1. Nature of Matter

• Characteristics of matter

• Physical and chemical properties

• Classification of matter

2. Laws of Chemical Combination

• Law of Conservation of Mass

• Law of Definite Proportions

• Law of Multiple Proportions

• Gay-Lussac's Law of Gaseous Volumes

• Avogadro's Law

3. Dalton's Atomic Theory

• Postulates

• Limitations

4. Atomic Mass

• Relative Atomic Mass

• Average Atomic Mass

• Molecular Mass

• Formula Mass

5. Mole Concept ⭐⭐⭐⭐⭐

Frequently Asked:

• Definition of Mole

• Avogadro Number

• Mole–Mass Relationship

• Mole–Volume Relationship

• Mole–Particles Relationship

6. Molar Mass

Frequently Asked:

• Gram Molecular Mass

• Gram Atomic Mass

• Conversion Problems

7. Percentage Composition

Frequently Asked:

• Percentage by Mass

• Numerical Problems

8. Empirical Formula

Frequently Asked:

• Determination from Percentage Composition

• Numerical Questions

9. Molecular Formula

Frequently Asked:

• Relation Between Empirical and Molecular Formula

• Molecular Formula Calculations

10. Stoichiometry ⭐⭐⭐⭐⭐

Frequently Asked:

• Balanced Chemical Equations

• Mole Ratio

• Limiting Reagent

• Excess Reagent

• Percentage Yield

• Atom Economy (Basic)

11. Concentration Terms

Frequently Asked:

• Molarity

• Molality

• Mole Fraction

• Mass Percentage

• Parts Per Million (PPM)

12. Significant Figures

Frequently Asked:

• Rules

• Addition & Subtraction

• Multiplication & Division

• Rounding Off

13. Scientific Notation

Frequently Asked:

• Exponential Form

• Unit Conversion

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⭐ Why This Chapter is Important?

This chapter carries significant weight in almost every entrance examination.

NEET

• Usually 1–2 questions every year.

• Mostly numerical and concept-based.

JEE Main

• Numerical calculations.

• Stoichiometry.

• Mole concept.

• Significant figures.

JEE Advanced

• Multi-concept numerical problems.

• Limiting reagent.

• Empirical & molecular formula.

• Advanced stoichiometry.

Board Examinations

• Definitions.

• Derivations.

• Numerical problems.

• Formula-based questions.

Common Mistakes Students Make

• Confusing mole and molar mass.

• Incorrect unit conversions.

• Errors in balancing equations.

• Ignoring significant figures.

• Wrong stoichiometric ratios.

• Mistakes while calculating empirical formula.

Preparation Tips

• Learn every formula thoroughly.

• Practice NCERT examples first.

• Solve previous year NEET questions.

• Practice at least 30–50 numerical problems.

• Revise dimensional analysis regularly.

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📊 Chapter Weightage

Examination	Expected Questions
NEET	1–2
JEE Main	1–2
JEE Advanced	1–2
CBSE Board	High
TN State Board	High

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🎯 High-Weightage Topics for NEET/JEE 2027

✅ Mole Concept

✅ Avogadro Constant

✅ Stoichiometry

✅ Empirical Formula

✅ Molecular Formula

✅ Percentage Composition

✅ Significant Figures

✅ Limiting Reagent

✅ Molarity

✅ Molality

✅ Mole Fraction

What is a Mole?

A mole is the SI unit for the amount of substance. One mole contains 6.022 × 10²³ elementary entities (atoms, molecules, ions, or electrons).

This number is called Avogadro's Number (Nₐ).

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Important Formulae

• Number of Moles = Mass / Molar Mass
• Mass = Number of Moles × Molar Mass
• Number of Particles = Number of Moles × 6.022 × 10²³
• Number of Moles = Number of Particles / 6.022 × 10²³
• At STP:
  • 1 mole of any gas = 22.4 L
• Density = Mass / Volume

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Molar Mass

Molar mass is the mass of one mole of a substance.

Examples:

• H₂ = 2 g mol⁻¹
• O₂ = 32 g mol⁻¹
• CO₂ = 44 g mol⁻¹
• H₂O = 18 g mol⁻¹
• NH₃ = 17 g mol⁻¹
• NaCl = 58.5 g mol⁻¹
• CaCO₃ = 100 g mol⁻¹
• H₂SO₄ = 98 g mol⁻¹

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Avogadro's Number

One mole contains:

• 6.022 × 10²³ atoms
• 6.022 × 10²³ molecules
• 6.022 × 10²³ ions
• 6.022 × 10²³ electrons

depending on the substance considered.

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MCQs (1–25)

1. One mole contains
A) 3.011 × 10²³ particles
B) 6.022 × 10²³ particles
C) 12.044 × 10²³ particles
D) 9.81 × 10²³ particles

2. SI unit of amount of substance is
A) Gram
B) Mole
C) Kilogram
D) Atom

3. Avogadro's number is
A) 6.022 × 10²²
B) 6.022 × 10²³
C) 3.011 × 10²³
D) 9.81 × 10²³

4. Molar mass of water is
A) 16
B) 17
C) 18
D) 20

5. Molar mass of CO₂ is
A) 40
B) 42
C) 44
D) 46

6. Number of moles in 18 g of water is
A) 0.5
B) 1
C) 2
D) 3

7. Number of moles in 44 g CO₂ is
A) 0.5
B) 1
C) 2
D) 4

8. One mole of helium contains
A) 6.022 × 10²³ atoms
B) 3.011 × 10²³ atoms
C) 12.044 × 10²³ atoms
D) 1.204 × 10²⁴ atoms

9. Mass of one mole of sodium is
A) 22 g
B) 23 g
C) 24 g
D) 46 g

10. Number of molecules in 2 moles of oxygen is
A) 6.022 × 10²³
B) 12.044 × 10²³
C) 18.066 × 10²³
D) 24.088 × 10²³

11. Molar mass of ammonia is
A) 16
B) 17
C) 18
D) 20

12. Number of moles in 98 g H₂SO₄
A) 0.5
B) 1
C) 2
D) 3

13. One mole of carbon atoms weighs
A) 6 g
B) 12 g
C) 14 g
D) 16 g

14. Molar mass of calcium carbonate is
A) 96
B) 98
C) 100
D) 102

15. Number of atoms in one mole of Na
A) 6.022 × 10²³
B) 3.011 × 10²³
C) 12.044 × 10²³
D) 9.81 × 10²³

16. Number of molecules in 0.5 mole H₂O
A) 6.022 × 10²³
B) 3.011 × 10²³
C) 12.044 × 10²³
D) 1.204 × 10²⁴

17. One mole of oxygen gas contains
A) 6.022 × 10²³ molecules
B) 6.022 × 10²³ atoms
C) 3.011 × 10²³ atoms
D) 12.044 × 10²³ molecules

18. Molar mass of NaCl is
A) 56.5
B) 57.5
C) 58.5
D) 59.5

19. Number of moles in 11 g CO₂
A) 0.25
B) 0.5
C) 1
D) 2

20. Number of molecules in one mole CH₄
A) 3.011 × 10²³
B) 6.022 × 10²³
C) 12.044 × 10²³
D) 1.204 × 10²⁴

21. Atomic mass of oxygen is
A) 8
B) 12
C) 16
D) 32

22. Molecular mass of O₂ is
A) 16
B) 24
C) 32
D) 64

23. Number of moles in 36 g H₂O
A) 1
B) 2
C) 3
D) 4

24. Number of atoms in one molecule of CO₂
A) 2
B) 3
C) 4
D) 5

25. Number of atoms present in one molecule of H₂SO₄
A) 5
B) 6
C) 7
D) 8

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Answer Key

1. B
2. B
3. B
4. C
5. C
6. B
7. B
8. A
9. B
10. B
11. B
12. B
13. B
14. C
15. A
16. B
17. A
18. C
19. A
20. B
21. C
22. C
23. B
24. B
25. C

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🚀 How to Score Full Marks from This Chapter

• Read every NCERT line carefully.

• Memorize all definitions.

• Learn all formulas.

• Practice unit conversions daily.

• Solve previous year NEET and JEE questions.

• Practice assertion–reason and statement-based questions.

• Revise important numerical problems before the exam.

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💬 Motivation Corner

"Success is the sum of small efforts, repeated day in and day out."
— Robert Collier

Meaning for NEET/JEE Aspirants:

No student becomes a topper overnight. Every MCQ you solve, every formula you revise, and every concept you understand brings you one step closer to your dream medical or engineering college. Stay consistent—small daily efforts create extraordinary results.

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Next Article: 50 Important Mole Concept MCQs with Detailed Answers & NEET Previous Year Questions