Chapter 1: Some Basic Concepts of Chemistry Assertion-Reason Questions | chemistry Class 11 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): The mass of a substance remains constant regardless of its location on Earth. Reason (R): Mass is the amount of matter present in a substance, while weight is the force exerted by gravity and varies with location.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): Molality of a solution does not change with temperature. Reason (R): Molality is defined as moles of solute per kilogram of solvent, and mass does not change with temperature.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 3

Logic Check

Assertion (A): Water is a homogeneous mixture of hydrogen and oxygen. Reason (R): Hydrogen and oxygen are present in water in a fixed ratio of 2:1 by volume.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): The Kelvin scale is preferred over the Celsius scale in thermodynamic calculations. Reason (R): The Kelvin scale starts at absolute zero and has no negative values, making it consistent with thermodynamic equations involving absolute temperature.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): Dalton's atomic theory could not explain Gay Lussac's Law of Gaseous Volumes. Reason (R): Dalton did not recognise the existence of polyatomic molecules, so he could not account for the simple volume ratios observed when gases react.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 6

Logic Check

Assertion (A): The number of significant figures in 0.200 g is three. Reason (R): Trailing zeros after a decimal point are significant as they indicate the precision of the measurement.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): Formula mass is used for sodium chloride (NaCl) instead of molecular mass. Reason (R): NaCl does not exist as discrete molecules but as a three-dimensional ionic lattice of Na⁺ and Cl⁻ ions, so the concept of a molecule does not apply.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): The components of a mixture can be separated by physical methods. Reason (R): In a mixture, the components are chemically bonded to each other and retain their individual properties.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 9

Logic Check

Assertion (A): Avogadro's Law was published but did not gain much support for about 50 years after its proposal. Reason (R): Avogadro's proposal was presented at the first international chemistry conference in Karlsruhe in 1811.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers. Reason (R): This is the Law of Multiple Proportions, proposed by John Dalton in 1803.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 11

Logic Check

Assertion (A): One mole of hydrogen gas (H₂) contains 6.022 × 10²³ hydrogen atoms. Reason (R): One mole of any substance contains 6.022 × 10²³ elementary entities, and the elementary entity for H₂ is the molecule H₂, not the atom H.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): Precision and accuracy always occur together in a good measurement. Reason (R): Precision refers to closeness of repeated measurements to each other, and accuracy refers to closeness of a measurement to the true value; these are independent properties.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): The average atomic mass of carbon is 12.011 u, not exactly 12 u. Reason (R): Carbon exists as three naturally occurring isotopes (¹²C, ¹³C, ¹⁴C) with different relative abundances, and the average atomic mass is a weighted mean based on these abundances.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): In a chemical reaction, the reactant that is present in excess always determines the amount of product formed. Reason (R): The limiting reagent is the reactant that is completely consumed first and limits the maximum amount of product that can be formed.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 15

Logic Check

Assertion (A): The SI system has seven base units. Reason (R): The SI system was established by the 11th General Conference on Weights and Measures (CGPM) in 1960 to provide a uniform system of measurement for the international scientific community.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): The empirical formula of glucose (C₆H₁₂O₆) is CH₂O. Reason (R): The empirical formula represents the simplest whole-number ratio of atoms in a compound; for C₆H₁₂O₆, the ratio C:H:O = 6:12:6 = 1:2:1.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 17

Logic Check

Assertion (A): Gases have neither definite shape nor definite volume. Reason (R): In gases, the particles are far apart with fast, easy movement and very weak intermolecular forces, causing them to completely fill any container.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 18

Logic Check

Assertion (A): In the multiplication 2.5 × 1.25, the result should be reported as 3.1. Reason (R): In multiplication, the result must not have more significant figures than the measurement with the greatest number of significant figures.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 19

Logic Check

Assertion (A): Acharya Kanda's atomic theory predates John Dalton's by approximately 2500 years. Reason (R): Acharya Kanda proposed his theory of Paramanu as a scientific theory grounded in experimental measurement of chemical laws.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): Molarity of a solution changes when the solution is heated. Reason (R): Volume of a solution increases with increase in temperature, thereby reducing the number of moles of solute per litre of solution.

Reasoning Options

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Chapter sections

Chapter 1: Some Basic Concepts of Chemistry | Assertion-Reason

Assertion (A): The mass of a substance remains constant regardless of its location on Earth. Reason (R): Mass is the amount of matter present in a substance, while weight is the force exerted by gravity and varies with location.

Assertion (A): Molality of a solution does not change with temperature. Reason (R): Molality is defined as moles of solute per kilogram of solvent, and mass does not change with temperature.

Assertion (A): Water is a homogeneous mixture of hydrogen and oxygen. Reason (R): Hydrogen and oxygen are present in water in a fixed ratio of 2:1 by volume.

Assertion (A): The Kelvin scale is preferred over the Celsius scale in thermodynamic calculations. Reason (R): The Kelvin scale starts at absolute zero and has no negative values, making it consistent with thermodynamic equations involving absolute temperature.

Assertion (A): Dalton's atomic theory could not explain Gay Lussac's Law of Gaseous Volumes. Reason (R): Dalton did not recognise the existence of polyatomic molecules, so he could not account for the simple volume ratios observed when gases react.

Assertion (A): The number of significant figures in 0.200 g is three. Reason (R): Trailing zeros after a decimal point are significant as they indicate the precision of the measurement.

Assertion (A): Formula mass is used for sodium chloride (NaCl) instead of molecular mass. Reason (R): NaCl does not exist as discrete molecules but as a three-dimensional ionic lattice of Na⁺ and Cl⁻ ions, so the concept of a molecule does not apply.

Assertion (A): The components of a mixture can be separated by physical methods. Reason (R): In a mixture, the components are chemically bonded to each other and retain their individual properties.

Assertion (A): Avogadro's Law was published but did not gain much support for about 50 years after its proposal. Reason (R): Avogadro's proposal was presented at the first international chemistry conference in Karlsruhe in 1811.

Assertion (A): When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers. Reason (R): This is the Law of Multiple Proportions, proposed by John Dalton in 1803.

Assertion (A): One mole of hydrogen gas (H₂) contains 6.022 × 10²³ hydrogen atoms. Reason (R): One mole of any substance contains 6.022 × 10²³ elementary entities, and the elementary entity for H₂ is the molecule H₂, not the atom H.

Assertion (A): Precision and accuracy always occur together in a good measurement. Reason (R): Precision refers to closeness of repeated measurements to each other, and accuracy refers to closeness of a measurement to the true value; these are independent properties.

Assertion (A): The average atomic mass of carbon is 12.011 u, not exactly 12 u. Reason (R): Carbon exists as three naturally occurring isotopes (¹²C, ¹³C, ¹⁴C) with different relative abundances, and the average atomic mass is a weighted mean based on these abundances.

Assertion (A): In a chemical reaction, the reactant that is present in excess always determines the amount of product formed. Reason (R): The limiting reagent is the reactant that is completely consumed first and limits the maximum amount of product that can be formed.

Assertion (A): The SI system has seven base units. Reason (R): The SI system was established by the 11th General Conference on Weights and Measures (CGPM) in 1960 to provide a uniform system of measurement for the international scientific community.

Assertion (A): The empirical formula of glucose (C₆H₁₂O₆) is CH₂O. Reason (R): The empirical formula represents the simplest whole-number ratio of atoms in a compound; for C₆H₁₂O₆, the ratio C:H:O = 6:12:6 = 1:2:1.

Assertion (A): Gases have neither definite shape nor definite volume. Reason (R): In gases, the particles are far apart with fast, easy movement and very weak intermolecular forces, causing them to completely fill any container.

Assertion (A): In the multiplication 2.5 × 1.25, the result should be reported as 3.1. Reason (R): In multiplication, the result must not have more significant figures than the measurement with the greatest number of significant figures.

Assertion (A): Acharya Kanda's atomic theory predates John Dalton's by approximately 2500 years. Reason (R): Acharya Kanda proposed his theory of Paramanu as a scientific theory grounded in experimental measurement of chemical laws.

Assertion (A): Molarity of a solution changes when the solution is heated. Reason (R): Volume of a solution increases with increase in temperature, thereby reducing the number of moles of solute per litre of solution.

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