Chemistry is the branch of science that studies composition, structure, properties, and transformations of matter.

Matter is anything that has mass and occupies space.

One mole contains \(6.022\times10^{23}\) entities.

State Avogadro’s number.

\(N_A = 6.022\times10^{23}\,mol^{-1}\).

Define atomic mass unit.

\(1\,u=\frac{1}{12}\)th mass of one \(^{12}C\) atom.

Average mass of atoms relative to \(1/12\)th of \(^{12}C\).

Define molecular mass.

Sum of atomic masses of all atoms in a molecule.

What is formula mass?

Sum of atomic masses in an ionic compound.

Write formula for molar mass.

Molar mass \(=\frac{\text{Mass}}{\text{Moles}}\).

Mass of one mole of substance in g mol\(^{-1}\).

What is percentage composition?

Mass percent of each element in a compound.

Write formula for mass percent.

\(\%\text{element}=\frac{\text{mass of element}}{\text{molar mass}}\times100\)

State law of conservation of mass.

Mass is neither created nor destroyed in a chemical reaction.

🧪 Chapter 1 · Class XI Chemistry

Some Basic Concepts
of Chemistry MCQs NCERT Chapter 1 — Class 11

Mole concept, stoichiometry, atomic & molecular mass, empirical formula, limiting reagent — the arithmetic foundations that every competitive exam builds upon. Master the calculations here; every subsequent chapter rewards you for it.

50 Questions Increasing Difficulty ~25 min NCERT-Mapped Numerical-Based Concept Boosters

📋 2026 Boards ⚡ JEE Mains 🔬 JEE Advanced 🩺 NEET

Easy

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🗓 Last Updated: February 2026 ✍️ By: Academia Aeternum Editorial Team ✅ Reviewed by: Subject Experts ⚡ Instant Feedback on Submit

🎯 Why Practice These MCQs

Some Basic Concepts of Chemistry is the compulsory gateway chapter for every competitive exam. JEE Mains repeats mole-concept numericals in almost every paper; NEET frequently pairs limiting reagent questions with concentration calculations. Students who skip this chapter's arithmetic precision consistently drop 4–8 marks across the paper — not just in this chapter.

⚛️ Mole Concept

⚖️ Stoichiometry

🧮 Limiting Reagent

📐 Empirical Formula

🔢 Atomic / Mol. Mass

💧 Concentration Units

📊 % Composition

🌡️ Significant Figures

📈 Exam Trend Analysis · Updated 2026

2024–25 JEE Mains papers showed a 35 % increase in multi-step mole calculations that chain atomic mass → moles → volume → concentration in a single question. NEET 2025 introduced two items requiring both empirical formula derivation and percentage yield in the same stem. NCERT language is preserved, but trap options now target unit-conversion errors and rounding at the intermediate step.

🎯 Knowledge Check

Chemistry — Some Basic Concepts Of Chemistry

50 Questions Class 11 MCQs

Which of the following best defines chemistry?
(Class XI – Basic Concept)

a a. Study of living organisms b b. Study of matter and its transformations c c. Study of energy only d d. Study of motion of bodies

Matter is anything that has:
(Class XI – Basic Concept)

a a. Only mass b b. Only volume c c. Mass and volume d d. Energy only

Which of the following is a physical change?
(Class XI – Conceptual)

a a. Rusting of iron b b. Burning of coal c c. Melting of ice d d. Digestion of food

The SI unit of amount of substance is:
(Class XI – Fundamentals)

a a. Gram b b. Mole c c. Kilogram d d. Litre

One mole of any substance contains:
(Class XI – Conceptual)

a a. \(6.022 \times 10^{22}\) particles b b. \(6.022 \times 10^{23}\) particles c c. \(3.011 \times 10^{23}\) particles d d. \(1.66 \times 10^{-24}\) particles

The mass of 1 mole of carbon-12 is:
(Class XI – Numerical)

a a. 6 g b b. 12 g c c. 1 g d d. 24 g

Which law states that mass is conserved during a chemical reaction?
(Class XI – Laws of Chemistry)

a a. Law of definite proportions b b. Law of multiple proportions c c. Law of conservation of mass d d. Avogadro’s law

The ratio by mass of elements in a compound is always:
(Class XI – Laws)

a a. Variable b b. Constant c c. Random d d. Zero

Which pair illustrates the law of multiple proportions?
(Class XI – Conceptual)

a a. NaCl and KCl b b. CO and CO2 c c. H2O and NaOH d d. NH3 and HCl

Atomic mass unit (amu) is defined relative to:
(Class XI – Fundamentals)

a a. Hydrogen atom b b. Oxygen atom c c. Carbon-12 atom d d. Nitrogen atom

The average atomic mass of chlorine is 35.5 due to:
(Class XI – Isotopes)

a a. Presence of ions b b. Presence of molecules c c. Presence of isotopes d d. Experimental error

Which of the following is an intensive property?
(Class XI – Properties of Matter)

a a. Mass b b. Volume c c. Density d d. Length

Density is defined as:
(Class XI – Formula Based)

a a. \(\frac{\text{mass}}{\text{volume}}\) b b. \(\frac{\text{volume}}{\text{mass}}\) c c. \(\text{mass} \times \text{volume}\) d d. \(\frac{1}{\text{mass}}\)

Which of the following is a derived SI unit?
(Class XI – Units)

a a. Kilogram b b. Metre c c. Second d d. Pascal

The number of significant figures in 0.00520 is:
(Class XI – Significant Figures)

a a. 2 b b. 3 c c. 4 d d. 5

Which measurement is most precise?
(Class XI – Data Analysis)

a a. 2.1 cm b b. 2.10 cm c c. 2.100 cm d d. 2 cm

The empirical formula represents:
(Class XI – Conceptual)

a a. Actual number of atoms b b. Simplest whole-number ratio of atoms c c. Structural arrangement d d. Molecular geometry

If the empirical formula mass equals molecular mass, the formula is:
(Class XI – Conceptual)

a a. Structural b b. Molecular c c. Ionic d d. Atomic

Molar mass of \(H_2SO_4\) is:
(Class XI – Numerical)

a a. 96 g mol\(^{-1}\) b b. 98 g mol\(^{-1}\) c c. 100 g mol\(^{-1}\) d d. 94 g mol\(^{-1}\)

The percentage of oxygen in water is approximately:
(Class XI – Numerical)

a a. 11% b b. 33% c c. 66% d d. 89%

One mole of any gas at STP occupies:
(Class XI – Gas Concept)

a a. 11.2 L b b. 22.4 L c c. 24.0 L d d. 44.8 L

The number of moles in 44 g of \(CO_2\) is:
(Class XI – Numerical)

a a. 0.5 b b. 1 c c. 2 d d. 4

Which quantity has no unit?
(Class XI – Conceptual)

a a. Mole fraction b b. Molarity c c. Molality d d. Density

Molarity depends on:
(Class XI – Conceptual)

a a. Temperature b b. Pressure c c. Nature of solute d d. Chemical formula

Molality is expressed as:
(Class XI – Formula)

a a. \(\frac{\text{moles of solute}}{\text{litres of solution}}\) b b. \(\frac{\text{moles of solute}}{\text{kg of solvent}}\) c c. \(\frac{\text{grams of solute}}{\text{litres of solvent}}\) d d. \(\frac{\text{mass of solution}}{\text{mass of solvent}}\)

Which is more reliable at varying temperatures?
(Class XI – Application)

a a. Normality b b. Molarity c c. Molality d d. Mole fraction

Limiting reagent determines:
(Class XI – Stoichiometry)

a a. Rate of reaction b b. Equilibrium constant c c. Amount of product formed d d. Activation energy

In a reaction, theoretical yield is:
(Class XI – Conceptual)

a a. Actual product obtained b b. Maximum possible product c c. Minimum product d d. Average product

Percentage yield is calculated as:
(Class XI – Formula)

a a. \(\frac{\text{theoretical}}{\text{actual}} \times 100\) b b. \(\frac{\text{actual}}{\text{theoretical}} \times 100\) c c. \(\frac{\text{product}}{\text{reactant}} \times 100\) d d. \(\frac{\text{reactant}}{\text{product}} \times 100\)

The dimensional formula of density is:
(Class XI – Advanced Basics)

a a. \(M^0L^0T^0\) b b. \(MLT^{-2}\) c c. \(ML^{-3}\) d d. \(M^2L^{-1}\)

If 2 moles of \(NaOH\) react with 1 mole of \(H_2SO_4\), the balanced equation is:
(Class XI – Stoichiometry)

a a. \(NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O\) b b. \(2NaOH + H_2SO_4 \rightarrow Na_2SO_4 + 2H_2O\) c c. \(NaOH + H_2SO_4 \rightarrow NaHSO_4 + H_2O\) d d. \(3NaOH + H_2SO_4 \rightarrow Na_3SO_4 + H_2O\)

Which has the maximum number of atoms?
(Class XI – Comparative)

a a. 1 mol \(H_2\) b b. 1 mol \(O_2\) c c. 1 mol \(O_3\) d d. 1 mol He

The smallest mass is of:
(Class XI – Numerical Concept)

a a. 1 mol \(H_2\) b b. 1 mol \(O_2\) c c. 1 mol \(N_2\) d d. 1 mol He

A solution containing 1 mol solute in 1 L solution is:
(Class XI – Concentration)

a a. 0.5 M b b. 1 M c c. 2 M d d. 1 m

The term stoichiometry refers to:
(Class XI – Conceptual)

a a. Measurement of heat b b. Study of reaction rates c c. Quantitative relationships in reactions d d. Study of atomic structure

Which error affects accuracy but not precision?
(Class XI – Experimental)

a a. Random error b b. Systematic error c c. Zero error d d. Parallax error

The mass percent of solute is:
(Class XI – Formula)

a a. \(\frac{\text{mass of solution}}{\text{mass of solute}} \times 100\) b b. \(\frac{\text{mass of solute}}{\text{mass of solution}} \times 100\) c c. \(\frac{\text{moles of solute}}{\text{mass of solution}} \times 100\) d d. \(\frac{\text{volume of solute}}{\text{volume of solution}} \times 100\)

Which quantity remains unchanged on dilution?
(Class XI – Conceptual)

a a. Molarity b b. Molality c c. Mole fraction of solute d d. Number of moles of solute

Avogadro’s law relates:
(Class XI – Gas Laws)

a a. Pressure and volume b b. Volume and temperature c c. Volume and number of moles d d. Pressure and temperature

The volume occupied by 0.5 mol of gas at STP is:
(Class XI – Numerical)

a a. 5.6 L b b. 11.2 L c c. 22.4 L d d. 44.8 L

Which is a state function?
(Class XI – Conceptual)

a a. Path length b b. Work c c. Heat d d. Mass

The mole fraction of solvent in a dilute solution is:
(Class XI – Reasoning)

a a. Zero b b. Less than solute c c. Greater than solute d d. Equal to solute

The limiting reagent is the reactant:
(Class XI – Application)

a a. With higher molar mass b b. Present in excess c c. Consumed first d d. With lowest density

Which measurement has highest relative error?
(Class XI – Numerical Reasoning)

a a. \(1.00 \pm 0.01\) b b. \(10.0 \pm 0.01\) c c. \(100 \pm 0.01\) d d. \(1000 \pm 0.01\)

The formula mass of \(NaCl\) refers to:
(Class XI – Ionic Compounds)

a a. Mass of one molecule b b. Mass of one ion pair c c. Average atomic mass d d. Empirical mass only

The term “significant figures” indicates:
(Class XI – Measurement)

a a. Accuracy only b b. Precision only c c. Reliability of measurement d d. Number of atoms

Which conversion factor is correct?
(Class XI – Units)

a a. \(1\ \text{L} = 10^3\ \text{cm}^3\) b b. \(1\ \text{L} = 10^2\ \text{cm}^3\) c c. \(1\ \text{L} = 1\ \text{cm}^3\) d d. \(1\ \text{L} = 10^6\ \text{cm}^3\)

The smallest unit that retains chemical identity is:
(Class XI – Fundamentals)

a a. Atom b b. Molecule c c. Ion d d. Element

If empirical formula is \(CH_2\) and molar mass is 42 g mol\(^{-1}\), molecular formula is:
(Class XI – Advanced Numerical)

a a. \(CH_2\) b b. \(C_2H_4\) c c. \(C_3H_6\) d d. \(C_4H_8\)

Stoichiometric coefficients in a balanced equation represent:
(NEET/JEE – Conceptual)

a a. Mass ratios only b b. Volume ratios only c c. Mole ratios d d. Energy ratios

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Chemistry Class 11 MCQs – Mole Concept | JEE & NEET 2026 — Complete Notes & Solutions · academia-aeternum.com

These 50 multiple-choice questions are carefully designed to reinforce and assess conceptual clarity in NCERT Class XI Chemistry Chapter 1 – Some Basic Concepts of Chemistry. The chapter lays the quantitative and philosophical foundation of chemistry, introducing students to the nature of matter, laws of chemical combination, mole concept, stoichiometry, units and measurements, significant figures, and concentration terms. The MCQs progress systematically from fundamental definitions and laws…

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Some Basic Concepts of Chemistry MCQs NCERT Chapter 1 — Class 11

Chemistry — Some Basic Concepts Of Chemistry

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