Chapter 3 of class 9 science as per the NCERT syllabus is Atoms And Molecules which deals with atoms, molecules, laws of chemical combination, atomic theory, chemical symbols, atomic mass, ions, valency, chemical formulas, molecular mass, formula unit mass, etc.
Here, we have discussed 30 Multiple Choice Questions based on these topics of the chapter. These questions will help you to learn more about the chapter and test your knowledge.
For each question below, there are four options out of which only one option is correct. The correct answer to each question is given at the end for your reference.
MCQ on Class 9 Science Chapter 3
1. What did Maharishi Kanad postulate regarding the nature of matter?
A) Matter is infinitely divisible
B) Matter consists of tiny indivisible particles called Parmanu
C) Matter can be transformed into energy
D) Matter is composed of four elements
2. Who among the following philosophers suggested the concept of indivisible particles called atoms?
A) Maharishi Kanad
B) Democritus
C) Antoine Lavoisier
D) John Dalton
3. Who laid the foundation of the chemical sciences by establishing the Law of Conservation of Mass?
A) Antoine Lavoisier
B) Maharishi Kanad
C) John Dalton
D) Democritus
4. According to the Law of Conservation of Mass, what happens to the mass during a chemical reaction?
A) Mass increases
B) Mass decreases
C) Mass remains constant
D) Mass becomes unpredictable
5. Which law states that elements combine in fixed proportions by mass to form compounds?
A) Law of Conservation of Mass
B) Law of Constant Proportions
C) Law of Multiple Proportions
D) Law of Definite Proportions
6. Who provided the basic theory about the nature of matter through his atomic theory?
A) Antoine Lavoisier
B) Democritus
C) John Dalton
D) Maharishi Kanad
7. According to Dalton’s atomic theory, atoms of a given element are:
A) Identical in mass and chemical properties
B) Different in mass and chemical properties
C) Indivisible particles
D) Capable of being created and destroyed
8. Which postulate of Dalton’s atomic theory explains the Law of Conservation of Mass?
A) Atoms are indivisible particles
B) Atoms of different elements have different masses
C) Atoms of a given element are identical in mass
D) Atoms combine in small whole-number ratios
9. What is the relative size of an atom compared to a molecule of water?
A) Larger
B) Same
C) Smaller
D) Cannot be compared
10. What unit is used to measure atomic radius?
A) Millimeter
B) Nanometer
C) Micrometer
D) Angstrom
11. Who suggested that symbols of elements should be made from one or two letters of the name of the element?
A) Antoine Lavoisier
B) John Dalton
C) Berzelius
D) Democritus
12. What is the modern-day symbol of sodium?
A) S
B) So
C) Na
D) No
13. What does the atomic mass unit (u) represent?
A) Mass of one mole of atoms
B) Mass of one atom of hydrogen
C) Mass of one atom of carbon-12
D) Mass of one gram of hydrogen
14. How many atoms are present in a molecule of oxygen gas (O2)?
A) 1
B) 2
C) 3
D) 4
15. What is the chemical formula for magnesium chloride?
A) MgCl
B) MgCl2
C) Mg2Cl
D) Mg2Cl2
16. What is the formula unit mass of Na2CO3?
A) 106 u
B) 110 u
C) 122 u
D) 150 u
17. How many atoms are present in a molecule of hydrogen sulfide (H2S)?
A) 1
B) 2
C) 3
D) 4
18. Which compound has the chemical formula NaNO3?
A) Sodium nitrate
B) Nitrogen oxide
C) Sodium nitrite
D) Nitric acid
19. What is the molecular mass of CO2?
A) 16 u
B) 28 u
C) 44 u
D) 48 u
20. Which law states that during a chemical reaction, mass can neither be created nor destroyed?
A) Law of Conservation of Mass
B) Law of Constant Proportions
C) Law of Multiple Proportions
D) Law of Definite Proportions
21. What is the atomic mass of oxygen?
A) 12 u
B) 14 u
C) 16 u
D) 18 u
22. What is the formula unit mass of K2CO3?
A) 106 u
B) 138 u
C) 156 u
D) 174 u
23. Which compound has the chemical formula CH4?
A) Carbon monoxide
B) Methane
C) Carbon dioxide
D) Carbon tetrachloride
24. According to Dalton’s atomic theory, what is the relative number and kinds of atoms in a given compound?
A) Constant
B) Variable
C) Increasing
D) Decreasing
25. What is the atomic mass of carbon-12?
A) 12 u
B) 14 u
C) 16 u
D) 18 u
26. What is the formula unit mass of ZnO?
A) 65 u
B) 81 u
C) 97 u
D) 112 u
27. Which postulate of Dalton’s atomic theory explains the Law of Definite Proportions?
A) Atoms are indivisible particles
B) Atoms of different elements have different masses
C) Atoms of a given element are identical in mass
D) Atoms combine in small whole-number ratios
28. What is the molecular mass of methane (CH4)?
A) 12 u
B) 14 u
C) 16 u
D) 18 u
29. What is the valency of oxygen?
A) 1
B) 2
C) 3
D) 4
30. What is the formula unit mass of Na2O?
A) 46 u
B) 62 u
C) 78 u
D) 94 u
Correct Answers
Here is the list of correct answers to the above questions.
- B) Matter consists of tiny indivisible particles called Parmanu
- B) Democritus
- A) Antoine Lavoisier
- C) Mass remains constant
- D) Law of Definite Proportions
- C) John Dalton
- A) Identical in mass and chemical properties
- A) Atoms are indivisible particles
- C) Smaller
- B) Nanometer
- C) Berzelius
- C) Na
- C) Mass of one atom of carbon-12
- B) 2
- B) MgCl2
- A) 106 u
- B) 2
- A) Sodium nitrate
- C) 44 u
- A) Law of Conservation of Mass
- C) 16 u
- C) 156 u
- B) Methane
- A) Constant
- A) 12 u
- D) 112 u
- D) Atoms combine in small whole-number ratios
- C) 16 u
- B) 2
- D) 94 u
The Bottom Line
I hope these 30 MCQs on Atoms And Molecules of Class 9 Science Chapter 3 have helped you in your studies and preparation.
If you have any queries, or comments or find any mistake in the above questions, feel free to contact me in the comment section below.
I would love to hear from you.
Abdur Rohman is an Electrical Engineer from Charaideo, Assam, who wears multiple hats as a part-time teacher, blogger, entrepreneur, and digital marketer. Passionate about education, he founded The Assam School blog to provide free, comprehensive textbook solutions, MCQs (Multiple Choice Questions), and other academic content for students from Class V to XII.