Class 9 Science Chapter 9 | MCQ

NCERT Class 9 Science MCQ | Chapter 9: Atomic Foundation of Matter

1. According to the Law of Conservation of Mass, mass can:
(A) Be created during a chemical reaction
(B) Be destroyed during a chemical reaction
(C) Neither be created nor destroyed in a chemical reaction
(D) Always increase during a reaction
Answer: (C)

2. The Law of Conservation of Mass was proposed by:
(A) Joseph Proust
(B) Antoine Lavoisier
(C) John Dalton
(D) Niels Bohr
Answer: (B)

3. Antoine Lavoisier is known as the:
(A) Father of Modern Chemistry
(B) Father of Atomic Physics
(C) Father of Biology
(D) Father of Nuclear Physics
Answer: (A)

4. In a closed system, the total mass of reactants is:
(A) Greater than the mass of products
(B) Less than the mass of products
(C) Equal to the mass of products
(D) Always zero
Answer: (C)

5. When baking soda reacts with vinegar, the gas produced is:
(A) Oxygen
(B) Hydrogen
(C) Carbon dioxide
(D) Nitrogen
Answer: (C)

6. In the first experimental setup involving vinegar and baking soda, the final mass differs from the initial mass mainly because:
(A) The vinegar disappears
(B) The baking soda loses mass
(C) The gas produced escapes
(D) The balance stops working
Answer: (C)

7. In the modified setup with a balloon attached to the flask, the final reading:
(A) Is much greater than the initial reading
(B) Matches the initial reading within experimental error
(C) Becomes zero
(D) Is always half the initial reading
Answer: (B)

8. The Law of Conservation of Mass applies to:
(A) Only physical changes
(B) Only reactions involving gases
(C) Every chemical reaction
(D) Only reactions involving solids
Answer: (C)

9. When sodium sulfate solution reacts with barium chloride solution, the precipitate formed is:
(A) Sodium chloride
(B) Barium sulfate
(C) Sodium sulfate
(D) Barium chloride
Answer: (B)

10. The Law of Constant Proportions was proposed by:
(A) Antoine Lavoisier
(B) John Dalton
(C) Joseph Proust
(D) J. J. Thomson
Answer: (C)

11. The Law of Constant Proportions is also called the:
(A) Law of Definite Proportions
(B) Law of Conservation of Energy
(C) Law of Multiple Volumes
(D) Law of Gravitation
Answer: (A)

12. According to the Law of Constant Proportions, elements in a compound combine in:
(A) Any ratio by mass
(B) A fixed ratio by mass
(C) Equal volumes only
(D) Random proportions
Answer: (B)

13. Hydrogen and oxygen are present in pure water in the mass ratio:
(A) 1:4
(B) 1:6
(C) 1:8
(D) 2:1
Answer: (C)

14. If 9 g of pure water is decomposed, the masses of hydrogen and oxygen obtained are:
(A) 4 g and 5 g
(B) 1 g and 8 g
(C) 2 g and 7 g
(D) 3 g and 6 g
Answer: (B)

15. Sodium chloride contains sodium and chlorine in the mass ratio:
(A) 1:1
(B) 23:35.5
(C) 35.5:23
(D) 2:1
Answer: (B)

16. If 46 g of sodium reacts completely to form sodium chloride, the mass of chlorine required is:
(A) 35.5 g
(B) 46 g
(C) 71 g
(D) 92 g
Answer: (C)

17. John Dalton proposed his atomic theory in:
(A) 1789
(B) 1808
(C) 1815
(D) 1897
Answer: (B)

18. According to Dalton’s atomic theory, all matter is made up of tiny particles called:
(A) Molecules
(B) Ions
(C) Atoms
(D) Nuclei
Answer: (C)

19. According to Dalton’s original theory, atoms were considered:
(A) Divisible in chemical reactions
(B) Indivisible particles
(C) Made only of electrons
(D) Made only of neutrons
Answer: (B)

20. According to Dalton, atoms of the same element have:
(A) Different chemical properties
(B) Identical mass and chemical properties
(C) Different valencies always
(D) Different chemical symbols
Answer: (B)

21. According to Dalton, atoms of different elements have:
(A) The same mass
(B) The same chemical properties
(C) Different masses and chemical properties
(D) The same number of electrons always
Answer: (C)

22. According to Dalton’s theory, atoms combine to form compounds in:
(A) Random ratios
(B) Simple whole-number ratios
(C) Fractional ratios only
(D) Equal ratios only
Answer: (B)

23. During a chemical reaction, according to Dalton’s theory, atoms:
(A) Are destroyed
(B) Are created
(C) Merely rearrange
(D) Change into energy
Answer: (C)

24. A molecule is an electrically:
(A) Positive entity
(B) Negative entity
(C) Neutral entity
(D) Charged entity
Answer: (C)

25. A molecule is capable of:
(A) Independent existence
(B) Existing only inside a nucleus
(C) Carrying a positive charge
(D) Existing only in solids
Answer: (A)

26. Which of the following is a molecule of an element?
(A) HCl
(B) H2
(C) H2O
(D) NaCl
Answer: (B)

27. The bond formed by sharing electrons between atoms is called:
(A) Ionic bond
(B) Covalent bond
(C) Metallic bond
(D) Nuclear bond
Answer: (B)

28. A hydrogen molecule, H2, is formed by:
(A) Transfer of one electron from one hydrogen atom to another
(B) Sharing one electron by each hydrogen atom
(C) Transfer of two protons
(D) Sharing two neutrons
Answer: (B)

29. A chlorine atom has how many electrons in its valence shell?
(A) 5
(B) 6
(C) 7
(D) 8
Answer: (C)

30. The chlorine molecule, Cl2, contains:
(A) One shared pair of electrons
(B) Two shared pairs of electrons
(C) Three shared pairs of electrons
(D) Four shared pairs of electrons
Answer: (A)

31. The oxygen molecule, O2, contains:
(A) A single covalent bond
(B) A double covalent bond
(C) A triple covalent bond
(D) An ionic bond
Answer: (B)

32. The chemical formula of hydrogen chloride is:
(A) H2Cl
(B) HCl
(C) HCl2
(D) H2Cl2
Answer: (B)

33. Hydrogen chloride is a covalent compound because:
(A) Hydrogen transfers an electron to chlorine
(B) Chlorine transfers an electron to hydrogen
(C) Hydrogen and chlorine share electrons
(D) Both atoms lose their electrons
Answer: (C)

34. The chemical formula of water is:
(A) HO
(B) H2O
(C) H2O2
(D) HO2
Answer: (B)

35. One molecule of water contains:
(A) One hydrogen atom and two oxygen atoms
(B) Two hydrogen atoms and one oxygen atom
(C) Two hydrogen atoms and two oxygen atoms
(D) One hydrogen atom and one oxygen atom
Answer: (B)

36. The force that holds atoms together is called a:
(A) Chemical bond
(B) Gravitational force
(C) Magnetic force
(D) Nuclear force
Answer: (A)

37. An ionic bond is formed by:
(A) Sharing of neutrons
(B) Sharing of protons
(C) Transfer of electrons
(D) Transfer of nuclei
Answer: (C)

38. When sodium loses one electron, it forms:
(A) Na-
(B) Na+
(C) Na2+
(D) Na2-
Answer: (B)

39. When chlorine gains one electron, it forms:
(A) Cl+
(B) Cl2+
(C) Cl-
(D) Cl2-
Answer: (C)

40. Positively charged ions are called:
(A) Anions
(B) Cations
(C) Molecules
(D) Isotopes
Answer: (B)

41. Negatively charged ions are called:
(A) Cations
(B) Anions
(C) Molecules
(D) Nucleons
Answer: (B)

42. Cations and anions are collectively called:
(A) Molecules
(B) Isotopes
(C) Ions
(D) Elements
Answer: (C)

43. The electrostatic attraction between oppositely charged ions is called:
(A) Covalent bond
(B) Ionic bond
(C) Metallic bond
(D) Nuclear bond
Answer: (B)

44. In sodium chloride, each sodium ion is surrounded by:
(A) Two chloride ions
(B) Four chloride ions
(C) Six chloride ions
(D) Eight chloride ions
Answer: (C)

45. Which of the following is a polyatomic ion?
(A) Na+
(B) Cl-
(C) Mg2+
(D) SO4^2-
Answer: (D)

46. Which of the following is the correct formula for magnesium hydroxide?
(A) MgOH
(B) Mg(OH)2
(C) Mg2OH
(D) Mg2(OH)
Answer: (B)

47. Which of the following is the correct formula for aluminium sulfate?
(A) AlSO4
(B) Al2SO4
(C) Al(SO4)2
(D) Al2(SO4)3
Answer: (D)

48. The molecular mass of water (H2O), taking H = 1 u and O = 16 u, is:
(A) 16 u
(B) 17 u
(C) 18 u
(D) 20 u
Answer: (C)

49. The formula unit mass of sodium oxide (Na2O), taking Na = 23 u and O = 16 u, is:
(A) 39 u
(B) 46 u
(C) 55 u
(D) 62 u
Answer: (D)

50. The formula unit mass of calcium nitrate, Ca(NO3)2, taking Ca = 40 u, N = 14 u and O = 16 u, is:
(A) 124 u
(B) 140 u
(C) 164 u
(D) 180 u
Answer: (C)

NCERT Class 9 Science MCQ | Chapter 9: Atomic Foundation of Matter

ASSERTION–REASON QUESTIONS

Q1. Assertion (A): The total mass remains unchanged during a chemical reaction when the system is closed.

Reason (R): Matter can neither be created nor destroyed in a chemical reaction.