Class 9 chemistry MCQs with answers are provided here for chapter 3 Atoms and Molecules. These MCQs are based on CBSE board curriculum and correspond to the most recent Class 9 chemistry syllabus. By practicing these Class 9 Multiple choice questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 9 Annual examinations as well as other entrance exams such as CTET and KVS. Here we can provide you with some multiple-choice questions based on the chapter "Atoms and Molecules" for Class 9 CBSE board syllabus. Please find the questions below:
1. What is the atomic number of an element?
a) The number of protons in the nucleus
b) The number of electrons in the nucleus
c) The sum of protons and neutrons in the nucleus
d) The number of neutrons in the nucleus
2. The mass number of an element is equal to:
a) The number of protons
b) The number of neutrons
c) The number of electrons
d) The number of protons and neutrons
3. Isotopes of an element have the same number of:
a) Electrons
b) Protons
c) Neutrons
d) Both (a) and (c)
4. The symbol H₂O represents:
a) One molecule of hydrogen and two molecules of oxygen
b) Two molecules of hydrogen and one molecule of oxygen
c) One atom of hydrogen and two atoms of oxygen
d) Two atoms of hydrogen and one atom of oxygen
5. The molecular formula of ammonia is:
a) NH₄
b) N₂H₄
c) NH₃
d) N₃H₃
6. How many moles of carbon atoms are present in one mole of methane (CH₄)?
a) 1 mole
b) 2 moles
c) 4 moles
d) 6 moles
7. Avogadro's constant is approximately equal to:
a) 6.02 x 10²³
b) 6.02 x 10⁻²³
c) 6.02 x 10⁻²²
d) 6.02 x 10²²
8. The molar mass of water (H₂O) is approximately:
a) 18 g/mol
b) 22 g/mol
c) 16 g/mol
d) 24 g/mol
9. Which of the following represents a cation?
a) Cl⁻
b) H⁺
c) O²⁻
d) N³⁻
10. The chemical formula of sodium carbonate is:
a) NaCO₂
b) NaHCO₃
c) Na₂CO₃
d) NaCO₃
11. The formula of carbon dioxide is:
a) CO
b) CO₂
c) C₂O
d) C₂O₂
12. How many atoms are present in one molecule of sulfuric acid (H₂SO₄)?
a) 4
b) 5
c) 6
d) 7
13. The valency of an element is determined by its:
a) Atomic number
b) Mass number
c) Number of protons
d) Number of electrons in the outermost shell
14. The chemical formula of calcium chloride is:
a) CaCl₂
b) CaCl
c) Ca₂Cl
d) CaCl₃
15. The empirical formula of a compound shows:
a) The actual number of atoms of each element in a molecule
b) The simplest whole-number ratio of atoms in a molecule
c) The molecular structure of the compound
d) The arrangement of atoms in the crystal lattice
16. What is the mass of one mole of oxygen atoms (O)?
a) 16 g
b) 32 g
c) 8 g
d) 24 g
17. Which of the following is a diatomic molecule?
a) Ozone (O₃)
b) Nitrogen (N₂)
c) Carbon monoxide (CO)
d) Methane (CH₄)
18. The law of conservation of mass was proposed by:
a) John Dalton
b) Dmitri Mendeleev
c) Antoine Lavoisier
d) J.J. Thomson
19. What is the percentage composition of hydrogen in water (H₂O)?
a) 11.11%
b) 22.22%
c) 55.56%
d) 88.89%
20. The chemical formula of baking soda is:
a) NaCl
b) NaHCO₃
c) Na₂CO₃
d) Na₂SO₄
21. The number of molecules in 18 g of water is approximately:
a) 6.02 x 10²³
b) 1.8 x 10²³
c) 3.01 x 10²³
d) 3.6 x 10²³
22. The mass of one mole of oxygen gas (O₂) is equal to:
a) 16 g
b) 32 g
c) 8 g
d) 24 g
23. The chemical formula of hydrochloric acid is:
a) H₂SO₄
b) HCl
c) HNO₃
d) H₂O
24. Which of the following is an anion?
a) Na⁺
b) Cl⁻
c) K⁺
d) Ca²⁺
25. The molecular formula of methane is:
a) CH₄
b) CH₃
c) C₂H₄
d) C₂H₆
26. The empirical formula of acetylene (a hydrocarbon) is:
a) C₂H₂
b) CH₄
c) C₆H₆
d) C₆H₁₂
27. The formula of nitric acid is:
a) H₂SO₄
b) HNO₃
c) HCl
d) H₃PO₄
28. The molar mass of carbon dioxide (CO₂) is approximately:
a) 22 g/mol
b) 16 g/mol
c) 44 g/mol
d) 12 g/mol
29. How many atoms are present in one molecule of glucose (C₆H₁₂O₆)?
a) 6
b) 12
c) 24
d) 18
30. The chemical formula of sulfuric acid is:
a) H₂SO₄
b) HNO₃
c) HCl
d) H₂O₄
Answers:
1. a) The number of protons in the nucleus
2. d) The number of protons and neutrons
3. d) Both (a) and (c)
4. d) Two atoms of hydrogen and one atom of oxygen
5. c) NH₃
6. c) 4 moles
7. a) 6.02 x 10²³
8. a) 18 g/mol
9. b) H⁺
10. c) Na₂CO₃
11. b) CO₂
12. c) 6
13. d) Number of electrons in the outermost shell
14. a) CaCl₂
15. b) The simplest whole-number ratio of atoms in a molecule
16. a) 16 g
17. b) Nitrogen (N₂)
18. c) Antoine Lavoisier
19. c) 55.56%
20. b) NaHCO₃
21. a) 6.02 x 10²³
22. b) 32 g
23. b) HCl
24. b) Cl⁻
25. a) CH₄
26. a) C₂H₂
27. b) HNO₃
28. c) 44 g/mol
29. b) 12
30. a) H₂SO₄