Matter and its nature; Dalton's atomic theory — NEET & JEE Questions

Question 1 · difficulty L1 · recall

According to Dalton's atomic theory, matter is composed of

• A. atoms
• B. only continuous fluid
• C. only ions
• D. only molecules with no atoms

Question 2 · difficulty L2 · understanding

Which statement is consistent with Dalton's atomic theory?

• A. Atoms of different elements are identical in mass and properties
• B. Atoms combine in simple whole-number ratios to form compounds
• C. Atoms can be created during ordinary chemical reactions
• D. A compound may contain its elements in any arbitrary mass ratio

Question 3 · difficulty L2 · understanding

Which modern observation shows that one statement of Dalton's original theory is not strictly correct?

• A. Existence of isotopes of an element with different masses
• B. Conservation of mass in ordinary chemical reactions
• C. Formation of compounds in simple ratios
• D. Existence of elements

Question 4 · difficulty L2 · understanding

Which statement best describes a chemical reaction in Dalton's atomic picture?

• A. Atoms are rearranged into new combinations
• B. Atoms disappear and new atoms are created
• C. Nuclei split in every chemical reaction
• D. Elements change their identities into other elements

Question 5 · difficulty L3 · application

Two compounds contain the same two elements. In the first, 1 g of element A combines with 2 g of B; in the second, 1 g of A combines with 4 g of B. Which law is illustrated?

• A. Law of multiple proportions
• B. Law of conservation of mass
• C. Avogadro's law
• D. Boyle's law

Question 6 · difficulty L3 · application

A compound always contains 40% element X and 60% element Y by mass, regardless of its source. Which principle does this observation support?

• A. Law of definite proportions
• B. Law of reciprocal proportions only
• C. Boyle's law
• D. Graham's law

Question 7 · difficulty L3 · application

If 12 g of carbon reacts completely with 32 g of oxygen to form carbon dioxide, what mass of carbon dioxide is expected according to conservation of mass?

• A. 20 g
• B. 32 g
• C. 44 g
• D. 56 g

Question 8 · difficulty L3 · application

A chemist finds that two samples labelled as the same pure compound contain different mass ratios of their constituent elements. What is the most direct conclusion?

• A. Both must still be the same pure compound
• B. At least one sample is not the same pure compound or is impure
• C. The law of definite proportions predicts such variation
• D. Dalton's theory requires arbitrary composition

Question 9 · difficulty L4 · application

Element A forms two oxides. In oxide I, 16 g of oxygen combine with 24 g of A. In oxide II, 32 g of oxygen combine with 24 g of A. What feature most strongly supports Dalton's atomic theory?

• A. The oxygen masses for fixed A are in the ratio 1:2
• B. The total masses are different
• C. Oxygen is a gas
• D. Both compounds must have identical formulas

Question 10 · difficulty L4 · application

Which statement correctly distinguishes a modern correction to Dalton's theory from a part that remains useful in ordinary chemistry?

• A. Atoms are indivisible in all circumstances, and isotopes do not exist
• B. Atoms contain subatomic particles, but ordinary chemical reactions still mainly involve rearrangement of atoms
• C. Atoms of the same element always have exactly the same mass, and chemical reactions create atoms
• D. Compounds have arbitrary composition, but atoms are conserved