Dalton's atomic theory (1808) proposed that all atoms of a given element have identical properties including identical mass, while atoms of different elements differ in mass. Dalton's theory could explain the laws of chemical combination, but it could not explain the laws of gaseous volumes.
-- NCERT Class 11 Chemistry, Ch. 1, p. 16Matter Dalton Atomic Theory
8 MCQs9-step worked example
Source: NCERT Some Basic Concepts of ChemistryPYQ coverage: NEET 2025Official key: NTA-verifiedLast updated: 8 Oct 2026
Try this first
Dalton's atomic theory could not explain which of the following?
- A.Law of conservation of mass
- B.Law of constant proportions
- C.Law of gaseous volumes
- D.Law of multiple proportions
Tap to see the answer
Answer: C. Dalton's theory could explain the laws of chemical combination but not the laws of gaseous volumes (NCERT Class 11 Chemistry, Chapter 1, page 16).
A is wrong: A is wrong because conservation of mass follows from proposal 4: atoms are neither created nor destroyed (NCERT Class 11 Chemistry, Chapter 1, page 16).
B is wrong: B is wrong because constant (definite) proportions follow from proposal 3: atoms combine in a fixed ratio (NCERT Class 11 Chemistry, Chapter 1, page 16).
D is wrong: D is wrong because multiple proportions is one of the laws of chemical combination that the theory explains (NCERT Class 11 Chemistry, Chapter 1, page 16).
Matter Dalton Atomic Theory, explained for NEET
What did Dalton's atomic theory fail to explain? The law of gaseous volumes, not the laws of mass. NEET 2025 asked exactly this, and the wrong options were the laws the theory does explain.
Matter. Anything which has mass and occupies space is called matter (NCERT Class 11 Chemistry, Chapter 1, page 4). It exists in three states. Solids have definite volume and definite shape, liquids have definite volume but take the shape of the container, and gases have neither definite volume nor definite shape (NCERT Class 11 Chemistry, Chapter 1, pages 4 and 5). The three states are interconvertible by changing temperature and pressure (NCERT Class 11 Chemistry, Chapter 1, page 5).
Classification. A pure substance has constituent particles all of the same chemical nature; a mixture contains particles of two or more pure substances in any ratio, so its composition is variable (NCERT Class 11 Chemistry, Chapter 1, page 5). A heterogeneous mixture has non-uniform composition (salt and sugar); components of a mixture separate by physical methods such as filtration, crystallisation and distillation (NCERT Class 11 Chemistry, Chapter 1, page 5). A pure substance has a fixed composition and its constituents cannot be separated by simple physical methods (NCERT Class 11 Chemistry, Chapter 1, page 5).
Dalton, 1808. (1) Matter consists of indivisible atoms. (2) All atoms of a given element have identical properties, including identical mass; atoms of different elements differ in mass. (3) Compounds form when atoms of different elements combine in a fixed ratio. (4) Chemical reactions are reorganisation of atoms, which are neither created nor destroyed (NCERT Class 11 Chemistry, Chapter 1, page 16).
The limit. The theory could explain the laws of chemical combination but not the laws of gaseous volumes, and it gave no reason for atoms combining (NCERT Class 11 Chemistry, Chapter 1, page 16).
Watch out: Proposal 1 calls the atom indivisible; Chapter 2 later shows it is not. A statement that Dalton "regarded the atom as the ultimate particle" is a true description of the theory.
How do you solve a Matter Dalton Atomic Theory question? A worked example
- 1
Given
Methane burns as CH₄ + 2O₂ → CO₂ + 2H₂O (the reaction NCERT writes in Chapter 1, page 20).
- 2
Required
Show that Dalton's proposal 4 holds: count the atoms of each element on both sides.
- 3
Concept
Chemical reactions are a reorganisation of atoms; atoms are neither created nor destroyed (NCERT Class 11 Chemistry, Chapter 1, page 16).
- 4
Formula
Atoms of an element = (molecules) × (atoms of that element per molecule), summed over one side.
- 5
Substitution
Left: CH₄ gives 1 C and 4 H; 2O₂ gives 2 × 2 O. Right: CO₂ gives 1 C and 2 O; 2H₂O gives 2 × 2 H and 2 × 1 O.
- 6
Calculation
Left: C = 1; H = 4; O = 2 × 2 = 4; total = 1 + 4 + 4 = 9 atoms. Right: C = 1; H = 2 × 2 = 4; O = 2 + 2 × 1 = 4; total = 1 + 4 + 4 = 9 atoms. The coefficients and subscripts are exact counting numbers and do not affect any significant-figure count.
- 7
Final answer
Carbon 1 = 1, hydrogen 4 = 4, oxygen 4 = 4: all atoms are conserved, with 9 atoms on each side.
- 8
Common trap
Balancing by changing a subscript (writing H₂O₂ for water) instead of the coefficient. Dalton's proposal 3 fixes the ratio of atoms in a compound; only the number of molecules can change.
- 9
Similar NEET-style question
Hydrogen and nitrogen combine as N₂ + 3H₂ → 2NH₃. Are the atoms conserved? (Answer: left = 2 N + 3 × 2 H = 2 + 6 = 8 atoms; right = 2 × (1 N + 3 H) = 2 × 4 = 8 atoms; N 2 = 2, H 6 = 6, so yes, atoms are only reorganised.)
---
Can you answer these Matter Dalton Atomic Theory MCQs?
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
MCQ 1Easy RecallPractice
Dalton's atomic theory could not explain which of the following?
Show answer and why every option is right or wrong
Answer: C. Dalton's theory could explain the laws of chemical combination but not the laws of gaseous volumes (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why A is wrong: A is wrong because conservation of mass follows from proposal 4: atoms are neither created nor destroyed (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why B is wrong: B is wrong because constant (definite) proportions follow from proposal 3: atoms combine in a fixed ratio (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why D is wrong: D is wrong because multiple proportions is one of the laws of chemical combination that the theory explains (NCERT Class 11 Chemistry, Chapter 1, page 16).
MCQ 2Easy RecallPractice
Matter is anything which:
Show answer and why every option is right or wrong
Answer: A. NCERT defines matter as anything which has mass and occupies space (NCERT Class 11 Chemistry, Chapter 1, page 4).
Why B is wrong: B is wrong because occupying space is half of the definition; both mass and space are needed (NCERT Class 11 Chemistry, Chapter 1, page 4).
Why C is wrong: C is wrong because matter must have mass as well as occupy space (NCERT Class 11 Chemistry, Chapter 1, page 4).
Why D is wrong: D is wrong because visibility is not part of the definition; air is matter although it is not seen (NCERT Class 11 Chemistry, Chapter 1, page 4).
MCQ 3Easy RecallPractice
According to Dalton's atomic theory, all atoms of a given element:
Show answer and why every option is right or wrong
Answer: D. Proposal 2: all atoms of a given element have identical properties, including identical mass (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why A is wrong: A is wrong because it is atoms of different elements that differ in mass (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why B is wrong: B is wrong because atoms are neither created nor destroyed in a chemical reaction (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why C is wrong: C is wrong because proposal 1 says matter consists of indivisible atoms (NCERT Class 11 Chemistry, Chapter 1, page 16).
MCQ 4Direct ApplicationPractice
Which state of matter has a definite volume but no definite shape?
Show answer and why every option is right or wrong
Answer: B. Liquids have definite volume but take the shape of the container in which they are placed (NCERT Class 11 Chemistry, Chapter 1, page 4).
Why A is wrong: A is wrong because solids have both a definite volume and a definite shape (NCERT Class 11 Chemistry, Chapter 1, page 4).
Why C is wrong: C is wrong because gases have neither definite volume nor definite shape (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why D is wrong: D is wrong because gases lack a definite volume, so only the liquid qualifies (NCERT Class 11 Chemistry, Chapter 1, page 5).
MCQ 5Direct ApplicationPractice
Which of the following is a heterogeneous mixture?
Show answer and why every option is right or wrong
Answer: D. A mixture of salt and sugar has non-uniform composition, so it is heterogeneous (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why A is wrong: A is wrong because sugar solution is a homogeneous mixture with uniform composition (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why B is wrong: B is wrong because air is a homogeneous mixture (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why C is wrong: C is wrong because glucose is a pure substance with fixed composition, not a mixture (NCERT Class 11 Chemistry, Chapter 1, page 5).
MCQ 6Direct ApplicationPractice
Which statement about Dalton's atomic theory is correct?
Show answer and why every option is right or wrong
Answer: C. Proposal 1 says matter consists of indivisible atoms (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why A is wrong: A is wrong because the three-particle structure came from later experiments; Dalton's proposal 1 treats the atom as indivisible (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why B is wrong: B is wrong because the theory could not explain the laws of gaseous volumes (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why D is wrong: D is wrong because atoms of different elements differ in mass (NCERT Class 11 Chemistry, Chapter 1, page 16).
MCQ 7CalculationPractice
Which statements are correct? (i) Components of a mixture can be separated by physical methods. (ii) Glucose can be separated into carbon, hydrogen and oxygen by filtration. (iii) A mixture has variable composition. (iv) A pure substance has fixed composition.
Show answer and why every option is right or wrong
Answer: B. (i) physical methods separate mixtures, (iii) a mixture's ratio is variable, (iv) a pure substance has fixed composition; (ii) is false because carbon, hydrogen and oxygen in glucose cannot be separated by simple physical methods (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why A is wrong: A is wrong because it includes (ii); filtration is a physical method and does not split glucose into its elements (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why C is wrong: C is wrong because it includes the false statement (ii) and drops the true statements (i) and (iv) (NCERT Class 11 Chemistry, Chapter 1, page 5).
Why D is wrong: D is wrong because it drops (iii), which is true: the ratio of components in a mixture may be any ratio (NCERT Class 11 Chemistry, Chapter 1, page 5).
MCQ 8CalculationPractice
In the reaction 2H₂ + O₂ → 2H₂O, 4 hydrogen atoms and 2 oxygen atoms react. According to Dalton, how many atoms of each kind are present in the products?
Show answer and why every option is right or wrong
Answer: A. Chemical reactions involve reorganisation of atoms, which are neither created nor destroyed; two molecules of water contain 2 × 2 = 4 hydrogen atoms and 2 × 1 = 2 oxygen atoms (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why B is wrong: B is wrong because no atom is destroyed in a chemical reaction (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why C is wrong: C is wrong because atoms are not lost; two H₂O molecules hold all 4 hydrogen atoms and both oxygen atoms (NCERT Class 11 Chemistry, Chapter 1, page 16).
Why D is wrong: D is wrong because atoms are not created in a reaction, so the totals cannot rise (NCERT Class 11 Chemistry, Chapter 1, page 16).
Free NEET study resources
Get a structured 30-day study plan and a complete formula booklet — delivered to your inbox instantly.
What to remember before solving Matter Dalton Atomic Theory questions
9 NCERT lines
Anything which has mass and occupies space is called matter. Everything around us, for example, book, pen, pencil, water, air, all living beings, etc., are composed of matter. You know that they have mass and they occupy space.
-- NCERT Class 11 Chemistry, Ch. 1, p. 4You are aware that matter can exist in three physical states viz. solid, liquid and gas. The constituent particles of matter in these three states can be represented as shown in Fig. 1.1. Particles are held very close to each other in solids in an orderly fashion and there is not much freedom of movement. In liquids, the particles are close to each other but they can move around. However, in gases, the particles are far apart as compared to those present in solid or liquid states and their movement is easy and fast. Because of such arrangement of particles, different states of matter exhibit the following characteristics: (i) Solids have definite volume and definite shape. (ii) Liquids have definite volume but do not have definite shape. They take the shape of the container in which they are placed.
-- NCERT Class 11 Chemistry, Ch. 1, p. 4(iii) Gases have neither definite volume nor definite shape. They completely occupy the space in the container in which they are placed. These three states of matter are interconvertible by changing the conditions of temperature and pressure. Solid liquid Gas On heating, a solid usually changes to a liquid, and the liquid on further heating changes to gas (or vapour). In the reverse process, a gas on cooling liquifies to the liquid and the liquid on further cooling freezes to the solid.
-- NCERT Class 11 Chemistry, Ch. 1, p. 5When all constituent particles of a substance are same in chemical nature, it is said to be a pure substance. A mixture contains many types of particles. A mixture contains particles of two or more pure substances which may be present in it in any ratio.
-- NCERT Class 11 Chemistry, Ch. 1, p. 5In contrast to this, in a heterogeneous mixture, the composition is not uniform throughout and sometimes different components are visible. For example, mixtures of salt and sugar, grains and pulses along with some dirt (often stone pieces), are heterogeneous mixtures.
-- NCERT Class 11 Chemistry, Ch. 1, p. 5It is worthwhile to mention here that the components of a mixture can be separated by using physical methods, such as simple hand-picking, filtration, crystallisation, distillation, etc.
-- NCERT Class 11 Chemistry, Ch. 1, p. 5Key Fact
Pure substances have fixed composition; constituents cannot be separated by simple physical methods
Pure substances have characteristics different from mixtures. Constituent particles of pure substances have fixed composition. Copper, silver, gold, water and glucose are some examples of pure substances. Glucose contains carbon, hydrogen and oxygen in a fixed ratio and its particles are of same composition. Hence, like all other pure substances, glucose has a fixed composition. Also, its constituents—carbon, hydrogen and oxygen—cannot be separated by simple physical methods.
-- NCERT Class 11 Chemistry, Ch. 1, p. 5In 1808, Dalton published ‘A New System of Chemical Philosophy’, in which he proposed the following : 1. Matter consists of indivisible atoms. 2. All atoms of a given element have identical properties, including identical mass. Atoms of different elements differ in mass. 3. Compounds are formed when atoms of different elements combine in a fixed ratio. 4. Chemical reactions involve reorganisation of atoms. These are neither created nor destroyed in a chemical reaction.
-- NCERT Class 11 Chemistry, Ch. 1, p. 16Matter Dalton Atomic Theory: NEET previous year questions (PYQs) with answers
1 question from NEET 2025, answers verified against NTA official keys
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)
Why the other options are wrong
- Option 2: Dalton's theory could explain the laws of chemical combination, including conservation of mass.
- Option 3: The law of constant proportion is a law of chemical combination, which Dalton's theory could explain.
- Option 4: Multiple proportion is a law of chemical combination, which Dalton's theory explained. It could not explain the laws of gaseous volumes.
All 12 past-paper questions from Some Basic Concepts of Chemistry →
More in Some Basic Concepts of Chemistry: 7 exam traps and mistakes · 3 formulas · 1 question pattern from its other lessons.
Sources
NCERT refs: Class 11 Chemistry Chapter 1, p.4 | Class 11 Chemistry Chapter 1, p.5 | Class 11 Chemistry Chapter 1, p.16
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
Every past-paper question from this chapter:
Practice the whole chapter →Prefer to watch this?
All 11 NEET PYQs of NCERT Class 11 Chemistry Chapter 1, in page order (17 min)
Watch on YouTube