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MCQs For Class 9 Science
Chapter 3 : Atoms and Molecules
MCQs For Class 9 Science Chapter 3 Atoms and Molecules
Q1. Who gave the Law of Conservation of Mass?
A. Antoine L. Lavoisier
B. Joseph L. Proust
C. John Dalton
D. Amedeo Avogadro
Correct Answer: A
Q2. "In a chemical substance, the elements are always present in definite proportions by mass." This is:
A. Law of Conservation of Mass
B. Law of Constant Proportions
C. Dalton's Atomic Theory
D. Mole Concept
Correct Answer: B
Q3. The ratio of Hydrogen and Oxygen in water (H₂O) by mass is:
A. 1:8
B. 8:1
C. 1:2
D. 2:1
Correct Answer: A
Q4. Who proposed the first meaningful Atomic Theory?
A. Ernest Rutherford
B. J.J. Thomson
C. John Dalton
D. Niels Bohr
Correct Answer: C
Q5. Which of the following is the symbol of Iron?
A. Ir
B. Fe
C. I
D. In
Correct Answer: B
Q6. The symbol of the element 'Sodium' is derived from its Latin name:
A. Natrium
B. Kalium
C. Ferrum
D. Argentum
Correct Answer: A
Q7. 1 nanometre (nm) is equal to:
A. 10⁻⁹ m
B. 10⁻⁸ m
C. 10⁹ m
D. 10⁻¹⁰ m
Correct Answer: A
Q8. Which of the following is used as a standard reference for measuring atomic masses?
A. Oxygen-16 atom
B. Hydrogen-1 atom
C. Carbon-12 atom
D. Nitrogen-14 atom
Correct Answer: C
Q9. The abbreviation IUPAC stands for:
A. International Union of Pure and Applied Chemistry
B. Internal United Physics and Chemistry
C. International Union of Public and Applied Chemistry
D. Indian Union of Pure and Applied Chemistry
Correct Answer: A
Q10. Atomicity of Oxygen (O₂) is:
A. Monoatomic
B. Diatomic
C. Triatomic
D. Polyatomic
Correct Answer: B
Q11. Which of the following is a monoatomic element?
A. Helium
B. Hydrogen
C. Phosphorus
D. Sulphur
Correct Answer: A
Q12. Atomicity of Phosphorus (P₄) is:
A. 1
B. 2
C. 3
D. 4
Correct Answer: D
Q13. Atomicity of Sulphur (S₈) is:
A. Diatomic
B. Tetra-atomic
C. Polyatomic
D. Monoatomic
Correct Answer: C
Q14. Molecules of metals and some other elements consist of only:
A. A single atom
B. Two atoms
C. Three atoms
D. Four atoms
Correct Answer: A
Q15. A negatively charged ion is called:
A. Cation
B. Anion
C. Atom
D. Molecule
Correct Answer: B
Q16. A positively charged ion is called:
A. Cation
B. Anion
C. Proton
D. Electron
Correct Answer: A
Q17. The chemical formula of Sodium Chloride is:
A. NaCl₂
B. Na₂Cl
C. NaCl
D. SCl
Correct Answer: C
Q18. What is the valency of Calcium (Ca)?
A. 1
B. 2
C. 3
D. 4
Correct Answer: B
Q19. The chemical formula of Magnesium Chloride is:
A. MgCl
B. Mg₂Cl
C. MgCl₂
D. Mg₂Cl₂
Correct Answer: C
Q20. Which of the following is a polyatomic ion?
A. Chloride (Cl⁻)
B. Oxide (O²⁻)
C. Ammonium (NH₄⁺)
D. Sodium (Na⁺)
Correct Answer: C
Q21. The formula of Aluminium Oxide is:
A. AlO
B. Al₂O
C. AlO₂
D. Al₂O₃
Correct Answer: D
Q22. The valency of Nitrogen in Ammonia (NH₃) is:
A. 1
B. 2
C. 3
D. 4
Correct Answer: C
Q23. The molecular mass of Water (H₂O) is:
A. 16 u
B. 18 u
C. 20 u
D. 10 u
Correct Answer: B
Q24. The molecular mass of Nitric Acid (HNO₃) is:
A. 63 u
B. 50 u
C. 48 u
D. 70 u
Correct Answer: A
Q25. The molecular mass of Carbon dioxide (CO₂) is:
A. 28 u
B. 32 u
C. 44 u
D. 40 u
Correct Answer: C
Q26. What is the value of the Avogadro Constant?
A. 6.022 × 10²²
B. 6.022 × 10²³
C. 6.022 × 10²⁴
D. 6.022 × 10⁻²³
Correct Answer: B
Q27. One mole of any substance contains how many particles?
A. 6.022 × 10²³
B. 10²³
C. 1.66 × 10⁻²⁴
D. 273
Correct Answer: A
Q28. The mass of 1 mole of Nitrogen atoms (N) is:
A. 7 g
B. 14 g
C. 28 g
D. 1 g
Correct Answer: B
Q29. How many moles are present in 52 g of Helium (He)? (Atomic mass of He = 4u)
A. 10
B. 13
C. 4
D. 52
Correct Answer: B
Q30. The molar mass of Oxygen molecule (O₂) is:
A. 16 g
B. 32 g
C. 8 g
D. 64 g
Correct Answer: B
Q31. Who introduced the term 'Mole'?
A. Wilhelm Ostwald
B. John Dalton
C. Avogadro
D. Newton
Correct Answer: A
Q32. The gram atomic mass of an element is also known as:
A. Atomic weight
B. Molar mass
C. Formula unit mass
D. Isotope mass
Correct Answer: B
Q33. What is the formula unit mass of NaCl? (Na=23, Cl=35 .5)
A. 58.5 u
B. 50 u
C. 60 u
D. 45.5 u
Correct Answer: A
Q34. The percentage of Calcium in Calcium Carbonate (CaCO₃) is: (Ca=40, C=12, O=16)
A. 12%
B. 48%
C. 40%
D. 100%
Correct Answer: C
Q35. The ratio of Nitrogen and Hydrogen in Ammonia (NH₃) by mass is:
A. 14:1
B. 14:3
C. 7:3
D. 3:14
Correct Answer: B
Q36. Which of the following contains the maximum number of molecules?
A. 1g of CO₂
B. 1g of N₂
C. 1g of H₂
D. 1g of CH₄
Correct Answer: C
Q37. The number of atoms in 0.5 moles of Carbon-12 is:
A. 6.022 × 10²³
B. 3.011 × 10²³
C. 12.044 × 10²³
D. 1.505 × 10²³
Correct Answer: B
Q38. Symbol of Gold is:
A. Gd
B. Ag
C. Au
D. Go
Correct Answer: C
Q39. Symbol of Potassium is:
A. Po
B. P
C. Pt
D. K
Correct Answer: D
Q40. Dalton's atomic theory could not explain:
A. Law of conservation of mass
B. Law of constant proportions
C. Isotopes and Isobars
D. Indivisibility of atoms
Correct Answer: C
Q41. Formula for Calcium Oxide is:
A. CaO
B. Ca₂O
C. CaO₂
D. Ca₂O₂
Correct Answer: A
Q42. How many atoms are present in a (PO₄)³⁻ ion?
A. 1
B. 4
C. 5
D. 3
Correct Answer: C
Q43. Chemical formula for Sodium Carbonate is:
A. NaCO₃
B. Na₂CO₃
C. Na(CO₃)₂
D. Na₃CO₂
Correct Answer: B
Q44. Which of the following is the mass of 0.2 moles of Oxygen atoms (O)?
A. 3.2 g
B. 16 g
C. 32 g
D. 1.6 g
Correct Answer: A
Q45. The mass of one molecule of Water is approximately:
A. 18 g
B. 18 u
C. 1 u
D. 3 × 10⁻²³ g
Correct Answer: B
Q46. Latin name for Copper is:
A. Ferrum
B. Cuprum
C. Kalium
D. Natrium
Correct Answer: B
Q47. Valency of Noble gases is:
A. 1
B. 2
C. 8
D. 0
Correct Answer: D
Q48. The number of atoms in a molecule is called its:
A. Valency
B. Atomic mass
C. Atomicity
D. Molarity
Correct Answer: C
Q49. Which of the following has mass equal to 1 mole?
A. 12g of C
B. 23g of Na
C. 35.5g of Cl
D. All of these
Correct Answer: D
Q50. Matter is made up of small particles called:
A. Bricks
B. Atoms
C. Cells
D. Tissues
Correct Answer: B