Dalton's atomic theory and concept of atom molecule element and compound - Question Bank

1. Which of the following is an example of a compound that violates the concept of atoms being indivisible?
A) Water (H₂O)
B) Carbon dioxide (CO₂)
C) Radioactive isotopes like Uranium-235
D) Ammonia (NH₃)
2. What is the primary role of Dalton's atomic theory in the development of chemistry?
A) It explained the existence of radioactivity.
B) It established the atomic basis of chemistry.
C) It discovered the electron and proton.
D) It defined the concept of a molecule.
3. The chemical symbol 'O' represents a(n):
A) Molecule of oxygen
B) Atom of oxygen
C) Compound
D) Mixture
4. Which of the following elements has atoms that are identical in mass and chemical properties according to Dalton's theory?
A) Carbon and Nitrogen
B) Oxygen and Sulfur
C) Iron and Iron
D) Hydrogen and Helium
5. The term 'atomos' from which 'atom' is derived, means:
A) Smallest
B) Indivisible
C) Fundamental
D) Burning
6. Dalton's theory postulated that atoms combine in a chemical reaction in:
A) Any ratio
B) Simple whole number ratios
C) Fractional ratios
D) Variable ratios
7. Which of the following is a molecular formula?
A) H₂O
B) Fe
C) NaCl
D) Cu
8. The discovery of the electron by J.J. Thomson in 1897 indicated that:
A) Atoms are indivisible.
B) Atoms are composed of smaller particles.
C) Elements are fundamental building blocks.
D) Compounds are formed by physical mixing.
9. A substance whose composition can vary is a(n):
A) Element
B) Compound
C) Mixture
D) Atom
10. What is the fundamental difference between an atom and a molecule of an element?
A) Atoms are indivisible, molecules are divisible.
B) Atoms are the smallest unit, molecules are formed by atoms.
C) Atoms are electrically charged, molecules are neutral.
D) Atoms exist independently, molecules do not.
11. Dalton's atomic theory was a landmark in chemistry because it:
A) Introduced the concept of subatomic particles.
B) Provided a quantitative basis for understanding chemical reactions.
C) Discovered radioactivity.
D) Explained the structure of the atom.
12. Which of the following is a pure substance?
A) Milk
B) Soil
C) Sugar
D) Air
13. The ratio of masses of hydrogen and oxygen in water (H₂O) is fixed. This supports the:
A) Law of Conservation of Mass
B) Law of Definite Proportions
C) Law of Multiple Proportions
D) Law of Reciprocal Proportions
14. Which of the following is a subatomic particle that contradicts Dalton's idea of indivisible atoms?
A) Proton
B) Neutron
C) Electron
D) All of the above
15. Dalton's theory proposed that all matter is composed of:
A) Molecules
B) Atoms
C) Elements
D) Compounds
16. What is the fundamental unit of a chemical compound?
A) Atom
B) Element
C) Molecule
D) Ion
17. If two elements form compounds A and B, and the mass of element Y combining with a fixed mass of element X in compound A is double the mass of element Y combining in compound B, this illustrates the Law of:
A) Conservation of Mass
B) Definite Proportions
C) Multiple Proportions
D) Reciprocal Proportions
18. According to Dalton's theory, atoms of different elements differ in:
A) Their indivisibility
B) Their mass and chemical properties
C) Their ability to combine
D) Their fundamental nature
19. The concept of 'element' as a fundamental substance was established by:
A) Dalton
B) Democritus
C) Lavoisier
D) Boyle
20. Which of the following is a characteristic of a compound?
A) Components can be easily separated.
B) Components retain their individual properties.
C) Components are chemically bonded in a fixed ratio.
D) Composition can vary.
21. What are the building blocks of elements according to Dalton's atomic theory?
A) Molecules
B) Compounds
C) Atoms
D) Ions
22. Dalton's atomic theory successfully explained:
A) The nature of subatomic particles
B) The radioactivity of elements
C) The laws of chemical combination
D) The origin of elements
23. The smallest unit of matter that exhibits the properties of a substance is:
A) Atom
B) Molecule
C) Compound
D) Element
24. Which of the following is NOT an element?
A) Carbon
B) Nitrogen
C) Sulfur
D) Glucose
25. The law that states that when two elements can combine to form more than one compound, the ratios of the masses of the second element which combine with a fixed mass of the first element are in simple whole numbers is:
A) Law of Conservation of Mass
B) Law of Definite Proportions
C) Law of Multiple Proportions
D) Gay-Lussac's Law of Combining Volumes
26. Which postulate of Dalton's atomic theory states that atoms cannot be created or destroyed in a chemical reaction?
A) Postulate 1
B) Postulate 2
C) Postulate 3
D) Postulate 4
27. In a mixture, the components retain their:
A) Original properties
B) New combined properties
C) Chemical identity
D) Physical state
28. Which of the following is an example of a mixture?
A) Water (H₂O)
B) Carbon dioxide (CO₂)
C) Air
D) Methane (CH₄)
29. A substance that is composed of two or more substances physically mixed together is called a(n):
A) Element
B) Compound
C) Mixture
D) Molecule
30. Dalton's atomic theory explains the formation of compounds based on the principle of:
A) Indivisibility of atoms
B) Combination of atoms in simple whole number ratios
C) Conservation of mass
D) Identical nature of atoms of the same element
31. The term 'molecule' was first introduced by:
A) Dalton
B) Avogadro
C) Lavoisier
D) Berzelius
32. Which of the following is a limitation of Dalton's atomic theory?
A) It explains the Law of Conservation of Mass.
B) It cannot explain the existence of isotopes.
C) It correctly defines elements and compounds.
D) It explains the formation of compounds.
33. The Law of Definite Proportions states that a given chemical compound always contains its component elements in a fixed ratio by:
A) Volume
B) Weight
C) Temperature
D) Pressure
34. Which of the following statements about molecules is NOT consistent with Dalton's atomic theory?
A) Molecules are formed by the combination of atoms.
B) Molecules of an element can be made of only one type of atom.
C) Molecules of a compound can be made of different types of atoms.
D) Molecules are the smallest particles that can exist independently.
35. According to Dalton's theory, what happens to the atoms of one element when they combine with atoms of another element?
A) They merge to form a new element.
B) They are rearranged to form compounds.
C) They are destroyed and new atoms are formed.
D) They remain separate and do not interact.
36. Dalton's atomic theory was proposed in the year:
A) 1776
B) 1808
C) 1905
D) 1666
37. The concept of 'atom' in ancient Greek philosophy was proposed by:
A) Aristotle
B) Democritus
C) Plato
D) Socrates
38. Which law is directly supported by Dalton's postulate that atoms combine in simple whole number ratios?
A) Law of Conservation of Mass
B) Law of Definite Proportions
C) Law of Multiple Proportions
D) Law of Reciprocal Proportions
39. The smallest particle of a compound that retains all its chemical properties is called a(n):
A) Atom
B) Element
C) Molecule
D) Ion
40. What is the smallest particle of an element that can exist independently and retain all its chemical properties?
A) Molecule
B) Atom
C) Compound
D) Ion
41. In a compound, the elements are present in a fixed ratio by:
A) Volume
B) Mass
C) Number of atoms
D) Density
42. Which of the following is an example of a compound?
A) Iron (Fe)
B) Gold (Au)
C) Ammonia (NH₃)
D) Helium (He)
43. A substance formed when two or more different chemical elements are chemically bonded together is known as a(n):
A) Element
B) Mixture
C) Compound
D) Atom
44. Which of the following is an example of an element?
A) Water (H₂O)
B) Salt (NaCl)
C) Oxygen (O₂)
D) Carbon dioxide (CO₂)
45. A substance that cannot be broken down into simpler substances by chemical means is called a(n):
A) Compound
B) Element
C) Mixture
D) Atom
46. What did Dalton propose about the conservation of atoms during a chemical reaction?
A) Atoms can be created or destroyed.
B) Atoms can be rearranged but not created or destroyed.
C) Atoms change their identity during a reaction.
D) Atoms are always conserved in mass but not in number.
47. According to Dalton, the smallest unit of matter that retains its chemical identity is the:
A) Molecule
B) Compound
C) Atom
D) Element
48. Which of the following postulates of Dalton's atomic theory was later modified by the discovery of isotopes?
A) Atoms are indivisible particles.
B) Atoms of a given element are identical in all respects.
C) Atoms of different elements are different in mass and chemical properties.
D) Atoms combine in simple whole number ratios to form compounds.
49. Dalton's atomic theory states that atoms of different elements:
A) Can combine in simple whole number ratios
B) Are always identical
C) Can never combine
D) Are different in mass and chemical properties
50. According to Dalton's atomic theory, atoms of a given element are:
A) Identical in all respects
B) Different in mass only
C) Identical in mass but different in chemical properties
D) Different in size but identical in mass
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