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CBSE Class 9  >  Class 9 Test  >  : Additional Practice  >  Test: Atoms and Molecules- Assertion & Reason Type Questions - Class 9 MCQ

Atoms and Molecules- Assertion & Reason Type Questions - Free AR with Solutions


MCQ Practice Test & Solutions: Test: Atoms and Molecules- Assertion & Reason Type Questions (15 Questions)

You can prepare effectively for Class 9 Class 9: Additional Practice with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Test: Atoms and Molecules- Assertion & Reason Type Questions". These 15 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: 30 minutes
  • - Number of Questions: 15

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Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 1
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Percentage of carbon in Na2CO3 is 11.32%.

Reason : % of Carbon = (Mass of carbon element / Molecular mass of Na2CO3) x 100

Detailed Solution: Question 1

% of carbon in the compound = (12/106) x 100 = 11.32%.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 2
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : When 10 g of CaCO3 is decomposed, 5.6 g of residue is left and 4.4 g of CO2 escapes.

Reason : Law of conservation of mass is followed.

Detailed Solution: Question 2

CaCO3 ​→ CaO + CO2 ​

100 gm 56 gm 44 gm

When 10g of CaCO3 is decomposed, 5.6g of residue is left and 4.4g of CO2 is escapes follows "Law of mass conservation".

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Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 3
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : One mole of molecules has mass equal to gram molecular mass and contains Avogadro’s number of molecules or has a volume of 22.4 L at STP if the substance is a gas.

Reason : One mole of an ionic compound has mass equal to gram formula unit mass and contains Avogadro’s number of formula units.

Detailed Solution: Question 3

Avogadro’s law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. This empirical relation can be derived from the kinetic theory of gases under the assumption of a perfect (ideal) gas. The law is approximately valid for real gases at sufficiently low pressures and high temperatures. At STP, all gas have same volume for 1 mol of gas and that volume is always equal to the 22.4 L.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 4
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : 1 amu equals to 1.6 x 10-24.

Reason : 1.66 x 10-24 g equals to1/12 th of mass of a C - 12 atom.

Detailed Solution: Question 4

1/12th of mass of 1 atom of C 12 - is 1.66 x 10-24 and atomic mass unit (1 amu) = 1.66 x 10-24 g.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 5
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Number of gram-molecules of SO2Cl2 in 13.5 g of sulfuryl chloride is 0.1.

Reason : Gram molecular mass is equal to one gram molecule.

Detailed Solution: Question 5

Gram molecular mass of, SO2Cl2 = 1 g molecule

135 g of SO2Cl2 = 1 g molecule [Since, GMM of SO2Cl2 = 135 g]

13.5 g of SO2Cl2 = 13.5/135 = 0.1 g molecule.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 6
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Pure water obtained from different sources such as river, well, spring, sea etc. always contains hydrogen and oxygen combined in the ratio of 1 : 8 by mass.

Reason : A chemical compound always contains same elements combined in same fixed proportion by mass.

Detailed Solution: Question 6

Pure water obtained from different sources such as river, well, spring, sea etc. always contain hydrogen and oxygen combined in the ratio 1 : 8 by mass. A chemical compound always contains elements combined together in same proportion by mass, it was discovered by French chemist, Joseph Proust (1799).

This illustrates the law of definite proportions.

Thus, both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 7
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : The molecular mass and formula unit mass of a substance is the sum of atomic masses of all the atoms in the molecular formula or formula unit of a compound.

Reason : The only difference between the molecular mass and formula unit mass is that, former is for molecular compounds (covalent compounds) and latter is for ionic compounds. However, their numerical value is the same.

Detailed Solution: Question 7

The number of protons in the nucleus of the atom is equal to the number of electrons revolving around the nucleus. More than two atoms combine to form the compound. Thus, the unit mass is equal to the sum of the atomic masses of all atoms in a formula unit of a compound.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 8
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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : One atomic mass unit (amu) is mass of an atom equal to exactly one-twelfth the mass of a carbon-12 atom.

Reason : Carbon-12 isotope was selected as standard.

Detailed Solution: Question 8

For universally accepted atomic mass unit in 1961, C- 12 was selected as standard. However, the new symbol used is ‘u’ (unified mass) in place of amu.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 9
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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Atomicity of O3 is 3

Reason : 1 mole of an element contains 6.023 x 1023 atoms.

Detailed Solution: Question 9

No. of atoms present in a molecules of a gaseous element is called atomicity.

For example, O2 ​has two atoms and hence its atomicity is 2.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 10
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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Molecular weight of SO2 is double to that O2.

Reason : One mole of SO2 contains double the number of molecules present in one mole of O2.

Detailed Solution: Question 10

Assertion (A) is true but reason (R) is false. Both, 1 mole of SO2 and 1 mole of O2 contain same number of molecules i.e., Avogadro’s number of molecules.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 11
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : A molecule is the smallest particle of an element or a compound which is capable of free existence.

Reason : The number of atoms present in one molecule of the substance is called its atomicity.

Detailed Solution: Question 11

Smallest particle of an element or a compound which is capable of independent existence is called molecule. A molecule is formed when two or more atoms join together chemically. Molecules of elements like noble gases such as helium,neon etc are made up of one atom only(molecules are capable of independent existence while atoms are not capable of independent existence). Only in these case atoms are capable of independent existence. Noble gases are monoatomic.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 12
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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Law of conservation of mass holds good for nuclear reactions.

Reason : It states that energy can neither be created nor destroyed in a chemical reaction.

Detailed Solution: Question 12

Law of conservation of mass does not hold good for nuclear reactions due to mass defect.

Law of conservation of mass states that matter can neither be created nor destroyed.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 13
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : 1 mole of H2 and O2 each occupy 22.4 Lat standard temperature and pressure.

Reason : Molar volume for all gases at the standard temperature and pressure has the same value.

Detailed Solution: Question 13

At a given temperature and pressure the volume of a gas is directly proportional to the amount of gas

V α n (P and T constant).

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 14
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Atomic mass of aluminium is 27.

Reason : An atom of aluminium is 27 times heavier than 1/12th of the mass of carbon-12 atom.

Detailed Solution: Question 14

Because atomic mass shows how many times an atom of that element is heavier than 1/12th of the mass of C-12 atom.

Test: Atoms and Molecules- Assertion & Reason Type Questions - Question 15
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Direction : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:

Assertion : Atomicity of oxygen is 2.

Reason : 1 mole of an element contains 6.023 x1023 atoms.

Detailed Solution: Question 15

Number of atoms present in a molecule of a gaseous element is called atomicity. e.g., O2 has two atoms and hence, its atomicity is 2.

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About this Class 9 Practice Test

This test contains 15 MCQs on Atoms and Molecules- Assertion & Reason Type Questions with detailed solutions for each question. It is part of the Class 9: Additional Practice course on EduRev, designed to align with the current Class 9 syllabus. Each solution explains not just the correct answer but also gives you an understanding of the topic — not just to attempt the question but also help you prepare for the exam with practice.

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