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Class 9 Chemistry Chapter 3 Atoms and Molecules MCQs

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

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