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CBSE Class 9  >  Class 9 Test  >  Science   >  Olympiad Test: Atoms and Molecules- 1 - Class 9 MCQ

Olympiad Test: Atoms and Molecules- 1 - Free MCQ with solutions Class 9


MCQ Practice Test & Solutions: Olympiad Test: Atoms and Molecules- 1 (10 Questions)

You can prepare effectively for Class 9 Science Class 9 with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Olympiad Test: Atoms and Molecules- 1". These 10 questions have been designed by the experts with the latest curriculum of Class 9 2026, to help you master the concept.

Test Highlights:

  • - Format: Multiple Choice Questions (MCQ)
  • - Duration: 20 minutes
  • - Number of Questions: 10

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Olympiad Test: Atoms and Molecules- 1 - Question 1
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The atomic theory of matter was proposed by

Detailed Solution: Question 1

The atomic theory of matter was proposed by John Dalton.

John Dalton (1766-1844) developed the first useful atomic theory of matter.

Olympiad Test: Atoms and Molecules- 1 - Question 2
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The atoms of which of the following pair of elements are most likely to exist in free state?

Detailed Solution: Question 2

The atoms of which are most likely to exist in free state are Helium and neon being inert gases having octet filled.

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Olympiad Test: Atoms and Molecules- 1 - Question 3
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Which of the following elements has the same molecular mass as its atomic mass?

Detailed Solution: Question 3

Neon is the element having same molecular mass as its atomic mass.

Actually, Neon would be listed as having an atomic mass of about 20.18, because of a mixture of isotopes, Z = Atomic number, the number of protons in the nucleus which defines the element.

Olympiad Test: Atoms and Molecules- 1 - Question 4
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The atomic number of an element X is 13. What will be the number of electrons in its ion X3+?

Detailed Solution: Question 4

X ⟶ X3+ means it loses three electrons, so X3+ = 10 electrons.

Olympiad Test: Atoms and Molecules- 1 - Question 5
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Kalium is the Latin name of

Detailed Solution: Question 5

Some symbols have been taken from the names of elements in Latin, German, or Greek. For example, symbol of potassium is K from its Latin name Kalium.

Olympiad Test: Atoms and Molecules- 1 - Question 6
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Certain mass of carbon burns with a given mass of oxygen to form certain mass of carbon mass of carbon dioxide, which law of chemical combination is used in this process of formation of compound

Detailed Solution: Question 6

First, let us write the reaction taking place here

C + O2 → CO2

As per the given condition, when 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced.

3g + 8g →11 g ( from the above reaction)

The total mass of reactants = mass of carbon + mass of oxygen

=3g+8g

=11g

The total mass of reactants = Total mass of products

Therefore, the law of conservation of mass is proved.

Then, it also depicts that the carbon dioxide contains carbon and oxygen in a fixed ratio by mass, which is 3:8.

Thus it further proves the law of constant proportions.

3 g of carbon must also combine with 8 g of oxygen only.

This means that (50−8)=42g of oxygen will remain unreacted.

The remaining 42 g of oxygen will be left un-reactive. In this case also, only 11 g of carbon dioxide will be formed

The above answer is governed by the law of constant proportions.

Olympiad Test: Atoms and Molecules- 1 - Question 7
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Which postulates of Dalton’s atomic theory gives laws of conservation of mass

Detailed Solution: Question 7

The postulate of Dalton’s atomic theory resulting from the law of conservation of mass is ‘The relative number and kinds of atoms are constant in a given compound. Atoms cannot be created nor destroyed in a chemical reaction’.

Olympiad Test: Atoms and Molecules- 1 - Question 8
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In water, hydrogen and oxygen are present in the ratio of

Detailed Solution: Question 8

H2O = 2 : 16 = 1 : 8

Olympiad Test: Atoms and Molecules- 1 - Question 9
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What is the mass of 0.2 mole of lead nitrate? (N=14, O=16, Pb=207)

Detailed Solution: Question 9

Gram Molecular weight of Pb(NO3)2

= 207 + (2 × 14) + 2 (16 × 3)

= 207 + 28 + 96

= 331

1 mole of Pb(NO3)2 is 331g

Therefore 0.2 mole of Pb(NO3)2 is 331 × 0.2

= 66.2 g

Olympiad Test: Atoms and Molecules- 1 - Question 10
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Find the total percentage of oxygen in magnesium nitrate crystal i.e., Mg(No3)2.6H2O (Atomic weight : H = 1, N = 14, O = 16, Mg = 24)

Detailed Solution: Question 10

Molecular weight of Mg(NO3)2.6H2O

= 24 + 2 (14 + 16 × 3) + 6(2 × 1 + 16)

= 24 + 124 + 108 = 256 amu

Atomic mass of oxygen in Mg(NO3)2.6H2O is,

= 2(16 × 3 × 6(16) = 96 + 96 = 192

% of oxygen = 192/256 × 100 = 75%

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