MCQ Basic Units of Matter Chapter 3 Class 9 Science

1. What are the building blocks of matter?

Compound

Molecules

Atoms

Element

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Question 1 of 14

2. How do atoms usually exist in nature?

In the form of molecules

In the form of ions

In the free state

In the form of molecules and Ions

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Question 2 of 14

3. Which atom is the smallest atom of all?

Lithium

Helium

Hydrogen

Carbon

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Question 3 of 14

4. Which of the following can be used to see atoms?

Scanning tunneling microscope

Microscope

Most powerful microscope

Optical microscope

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Question 4 of 14

5. The number of atoms present in one molecule of an element is called as:

Empirical formula

Molecule

Atomicity

Compound

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Question 5 of 14

6. Out of the following, which one is an example of a molecule of a compound?

Water molecule

Oxygen molecule

Ozone

Nitrogen molecule

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Question 6 of 14

7. Cl₂ stands for:

2 molecules of chlorine

2 atoms of chlorine

2 ions of chlorine

3 molecule of chlorine

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Question 7 of 14

8. Which constituent of air is monoatomic?

Argon

Water vapour

Oxygen

Nitrogen

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Question 8 of 14

9. Molecules can exist in free state because:

They are very stable.

They are electrically charged.

They are very reactive.

They are bigger in size as compared to atoms.

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Question 9 of 14

10. Which is the smallest particle of an element that can take part in a chemical reaction?

Molecule

Mixture

Compound

Atom

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Question 10 of 14

11. Assertion: Atoms always combine to form molecule and ions.
Reason: Atoms of most element are not able to exist independently.

a.) Both Assertion and Reason are correct, and reason is the correct explanation for assertion.

b.) Both Assertion and Reason are correct, and Reason is not the correct explanation for Assertion.

c.) Assertion is true but Reason is false.

d.) Assertion is false but Reason is true

Question 11 of 14

12. Assertion: Atomicity of ozone is three while that of oxygen is two.

Reason: Atomicity is the number of atoms constituting a molecule.

a.) Both Assertion and Reason are correct, and reason is the correct explanation for assertion.

b.) Both Assertion and Reason are correct, and Reason is not the correct explanation for Assertion.

c.) Assertion is true but Reason is false.

d.) Assertion is false but Reason is true

Question 12 of 14

13. Assertion : Molecular weight of oxygen is 16.
Reason : Atomic weight of oxygen is 16.

a.) Both Assertion and Reason are correct, and reason is the correct explanation for assertion.

b.) Both Assertion and Reason are correct, and Reason is not the correct explanation for Assertion.

c.) Assertion is true but Reason is false.

d.) Assertion is false but Reason is true

Question 13 of 14

14. Assertion : The number of moles of He in 52 g of He is 13.
Reason : The number of moles of an atom is the ratio of its given mass to its molar mass.

a.) Both Assertion and Reason are correct, and reason is the correct explanation for assertion.

b.) Both Assertion and Reason are correct, and Reason is not the correct explanation for Assertion.

c.) Assertion is true but Reason is false.

d.) Assertion is false but Reason is true

Question 14 of 14