What does Some Basic Concepts of Chemistry cover for NEET Chemistry?

5 lessons: Atomic Molecular Masses, Empirical Molecular Formulae, Laws Chemical Combination, Mole Concept and Stoichiometry.

How often has Some Basic Concepts of Chemistry come up in NEET past papers?

Our set of verified past papers has 12 questions from this unit, from NEET 2020, 2022, 2023, 2024, 2025 and 2026. Each is answered against the official NTA key.

Is the Some Basic Concepts of Chemistry material free?

Yes. All 5 lessons and 40 practice questions are free, with no login needed.

Some Basic Concepts of Chemistry

5 lessons

Topic index in NCERT order

5 of 5 lessons by the NCERT chapter they teach from, in book order. The page is the first printed page of your NCERT book the lesson cites; PYQs are the past NEET questions on that topic.

Class 11 Chemistry, Chapter 1

Atomic Molecular Masses

8 MCQs2 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Empirical Molecular Formulae

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Laws Chemical Combination

8 MCQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Mole Concept

8 MCQs4 PYQs3 revision cardsWorked example

Direct Application (4)Easy Recall (2)Calculation (1)Concept Trap (1)

Stoichiometry

8 MCQs4 PYQs6 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Past-paper questions from this unit

12 questions from NEET 2020, 2022, 2023, 2024, 2025, 2026. Answers verified against NTA official keys.

By year in our set: 2020 (2) · 2022 (1) · 2023 (2) · 2024 (3) · 2025 (2) · 2026 (2)

Lesson: Mole Concept

NEET 2026

The numbers 17.0145 and 21.0235 were rounded to three figures after the decimal point. The resulting numbers, respectively, are

117.014 and 21.023

217.015 and 21.023

317.014 and 21.024

417.015 and 21.024

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Stoichiometry

NEET 2026

The amount of carbon dioxide evolved upon complete combustion of 116 g of n-butane is (Given: atomic mass in amu H = 1, C = 12 and O = 16)

1352 g

2322 g

3176 g

4362 g

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Mole Concept

NEET 2025

Among the following, choose the ones with equal number of atoms. A. 212 g of Na2CO3(s) [molar mass = 106 g] B. 248 g of Na2O(s) [molar mass = 62 g] C. 240 g of NaOH(s) [molar mass = 40 g] D. 12 g of H2(g) [molar mass = 2 g] E. 220 g of CO2(g) [molar mass = 44 g] Choose the correct answer from the options given below :

1B, D, and E only

2A, B, and C only

3A, B, and D only

4B, C, and D only

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

NEET 2025

Dalton’s Atomic theory could not explain which of the following?

1Law of gaseous volume

2Law of conservation of mass

3Law of constant proportion

4Law of multiple proportion

NTA Answer: Option 1(final)

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Lesson: Stoichiometry

NEET 2024Revised key

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution, the mass of sodium hydroxide left unreacted is equal to

1750 mg

2250 mg

3Zero mg

4200 mg

NTA Answer: Option 2(revised_final)

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Lesson: Mole Concept

NEET 2024Revised key

The highest number of helium atoms is in

14 mol of helium

24 u of helium

34 g of helium

42.271098 L of helium at STP

NTA Answer: Option 1(revised_final)

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Lesson: Empirical Molecular Formulae

NEET 2024Revised key

A compound X contains 32% of A, 20% of B and remaining percentage of C. Then, the empirical formula of X is : (Given atomic masses of A = 64; B = 40; C = 32 u)

1A₂BC₂

2ABC₃

3AB₂C₂

4ABC₄

NTA Answer: Option 2(revised_final)

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Lesson: Stoichiometry

NEET 2023

The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40) [CaCO₃ —[1200 K]→ CaO + CO₂]

11.76 g

22.64 g

31.32 g

41.12 g

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

NEET 2023

Select the correct statements from the following A. Atoms of all elements are composed of two fundamental particles. B. The mass of the electron is 9.10939 × 10⁻³¹ kg. C. All the isotopes of a given element show same chemical properties: D. Protons and electrons are collectively known as nucleons. E. Dalton’s atomic theory, regarded the atom as an ultimate particles of matter Choose the correct answer from the options given below

1C, D and E only

2A and E only

3B, C and E only

4A, B and C only

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Stoichiometry

NEET 2022

What mass of 95% pure CaCO3 will be required to neutralise 50 mL of 0.5 M HCl solution according to the following reaction? CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + 2H2O(l) [Calculate upto second place of decimal point]

19.50 g

21.25 g

31.32 g

43.65 g

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

NEET 2020

The number of protons, neutrons and electrons in ¹⁷⁵₇₁Lu, respectively, are :

1175, 104 and 71

271, 104 and 71

3104, 71 and 71

471, 71 and 104

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: Mole Concept

NEET 2020

Which one of the followings has maximum number of atoms ?

11 g of Li(s) [Atomic mass of Li=7]

21 g of Ag(s) [Atomic mass of Ag=108]

31 g of Mg(s) [Atomic mass of Mg=24]

41 g of O2 (g) [Atomic mass of O=16]

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Exam traps and common mistakes in this unit

Lesson: Mole Concept

Trap

Mole-volume STP confusion

Category: Unit Conversion

Student uses a fixed molar volume (22.7 L/mol or 22.4 L/mol) at conditions it does not apply to, or mixes the two conventions.

When it triggers

Question gives gas at non-STP T or P.

How to avoid

One mole of an ideal gas occupies 22.7 L at 273.15 K and 1 bar (100 kPa), the value NCERT's reprint uses; 22.4 L is the older figure for 273.15 K and 1 atm (101.325 kPa). Use whichever matches the conditions the question states; for any other T or P, use PV = nRT.

Lesson: Stoichiometry

Trap

Limiting reagent by stoichiometric ratio

Category: Overthinking

Student picks reagent with smaller absolute moles as limiting, ignoring stoichiometric coefficients.

When it triggers

Stoichiometry problem with two reactants.

How to avoid

Compute (moles available / coefficient) for each. Smaller value = limiting reagent. Compare ratios, not raw moles.

Lesson: Stoichiometry

Trap

Limiting reagent identification

Category: Overthinking

Student computes from total mole amounts without checking stoichiometric ratios. Limiting reagent is the one that runs out first; rest is excess.

When it triggers

Stoichiometry problem with two reactants given.

How to avoid

Compare moles available to stoichiometric requirement. Compute moles_actual / coefficient for each; smaller value = limiting reagent.

Lesson: Stoichiometry

Trap

Percentage purity in mass-mole calculations

Category: Overthinking

Student forgets to multiply by purity% before computing moles from impure sample mass.

When it triggers

Question states sample is X% pure (e.g. limestone, ore).

How to avoid

Effective mass = sample mass × (purity/100). Then compute moles using effective mass / molar mass.

Lesson: Mole Concept

Mistake

Applies a fixed molar volume (22.7 or 22.4 L/mol) at conditions it does not apply to.

Root cause: concept gap

Correction

22.7 L/mol holds at 273.15 K and 1 bar (NCERT's value); 22.4 L/mol at 273.15 K and 1 atm. Use the one matching the stated conditions, otherwise PV = nRT.

Lesson: Stoichiometry

Mistake

Identifies limiting reagent by absolute moles, ignoring stoichiometry.

Root cause: concept gap

Correction

Compute (moles_actual / coefficient) for each reactant. Smaller value = limiting.

Lesson: Stoichiometry

Mistake

Forgets to apply purity% before mole calculation in impure-sample problems.

Root cause: concept gap

Correction

Effective mass = stated mass × (purity/100). Then convert to moles using molar mass.

Formulas in this unit

Lesson: Mole Concept

Number of moles

n = m / M = N / N_{A} = V /22.7 L

Three equivalent ways to compute moles: from mass and molar mass, from number of particles, from gas volume at 273.15 K and 1 bar.

Symbol	Quantity	SI Unit
n	moles	mol
m	mass	g
M	molar mass	g/mol
N	particle count	-
NA	Avogadro 6.022e23	1/mol
V	gas volume	L

Valid when

Use g/(g/mol) for mass route
22.7 L mol^-1 only at 273.15 K and 1 bar (22.4 L mol^-1 if the question uses 1 atm); otherwise PV = nRT
Pure substance

Lesson: Stoichiometry

Molality

m = n / m_{solv}

Molal concentration: moles of solute per kg of solvent. Temperature-independent.

Symbol	Quantity	SI Unit
m	molality	mol/kg
n	moles solute	mol

Valid when

Mass of SOLVENT (not solution)

Lesson: Stoichiometry

Molarity

M = n / V

Molar concentration: moles of solute per litre of solution.

Symbol	Quantity	SI Unit
M	molarity	mol/L
n	moles solute	mol
V	solution volume	L

Valid when

Volume of SOLUTION not solvent
Temperature dependent (volume changes with T)

NEET question patterns in this unit

Lesson: Mole Concept

Mole concept and stoichiometry calculations: mole-mass conversion, limiting reagent, percentage purity, % composition.

Direct ApplicationMedium

Common distractors

swapped classes

Tempts surface-level recall.

Questions about this unit

What does Some Basic Concepts of Chemistry cover for NEET Chemistry?: 5 lessons: Atomic Molecular Masses, Empirical Molecular Formulae, Laws Chemical Combination, Mole Concept and Stoichiometry.
How often has Some Basic Concepts of Chemistry come up in NEET past papers?: Our set of verified past papers has 12 questions from this unit, from NEET 2020, 2022, 2023, 2024, 2025 and 2026. Each is answered against the official NTA key.
Is the Some Basic Concepts of Chemistry material free?: Yes. All 5 lessons and 40 practice questions are free, with no login needed.