Chapter 1: Solutions Assertion-Reason Questions | chemistry Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): Molality is preferred over molarity for expressing concentrations in experiments involving temperature changes. Reason (R): Molality depends on the mass of solvent, which does not change with temperature, while molarity depends on volume, which changes with temperature.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): The vapour pressure of a solution of a non-volatile solute is always lower than that of the pure solvent at the same temperature. Reason (R): The presence of solute molecules reduces the fraction of solvent molecules at the surface, lowering the rate of evaporation.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): The boiling point of a solution is always higher than that of the pure solvent. Reason (R): The vapour pressure of a solution is lower than that of the pure solvent; therefore, a higher temperature is needed to make the vapour pressure equal to atmospheric pressure.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): Soft drink bottles are sealed under high pressure of CO₂. Reason (R): According to Henry's law, the solubility of CO₂ in water increases with increasing pressure, keeping more CO₂ dissolved in the drink.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 5

Logic Check

Assertion (A): Aquatic animals are more comfortable in cold water than in warm water. Reason (R): The solubility of oxygen in water is higher at lower temperatures because dissolution of gases is an exothermic process.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): The sum of mole fractions of all components in a solution is always equal to unity. Reason (R): Mole fraction of each component is defined as the ratio of its moles to the total moles of all components in the solution.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 7

Logic Check

Assertion (A): The relative lowering of vapour pressure is a colligative property. Reason (R): Relative lowering of vapour pressure depends on the number of solute particles relative to solvent molecules, irrespective of the nature of solute.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 8

Logic Check

Assertion (A): Ethanol-water solution shows positive deviation from Raoult's law. Reason (R): In ethanol-water mixture, the A-B (ethanol-water) interactions are stronger than A-A (ethanol-ethanol) or B-B (water-water) interactions.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 9

Logic Check

Assertion (A): The experimentally determined molar mass of KCl in water is lower than its true molar mass. Reason (R): KCl dissociates into K⁺ and Cl⁻ in water, increasing the number of particles in solution, which increases colligative properties, leading to a lower calculated molar mass.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): Osmotic pressure method is preferred for determining molar mass of polymers and proteins. Reason (R): Polymers and proteins have very large molar masses; the resulting osmotic pressure, though small, is large enough to be measured accurately at room temperature without degrading the biomolecule.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 11

Logic Check

Assertion (A): Pressure has no significant effect on the solubility of solids in liquids. Reason (R): Solids and liquids are nearly incompressible; their volumes (and hence solubility) remain essentially unaffected by changes in pressure.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 12

Logic Check

Assertion (A): The component present in the largest quantity in a solution is called the solvent. Reason (R): The solvent determines the physical state in which the solution exists.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 13

Logic Check

Assertion (A): Nitric acid-water mixture (68% HNO₃) forms a maximum boiling azeotrope at 393.5 K. Reason (R): HNO₃-water mixture shows large negative deviation from Raoult's law, resulting in a lower vapour pressure and hence a higher boiling point at the azeotropic composition.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): Solvent molecules always flow from lower concentration of solution to higher concentration during osmosis. Reason (R): Solvent molecules move from a region of higher chemical potential (pure solvent/dilute solution) to a region of lower chemical potential (concentrated solution).

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): An azeotropic mixture of ethanol and water cannot be further purified by fractional distillation beyond ~95% ethanol. Reason (R): At the azeotropic composition, the liquid and vapour phases have identical compositions, so no enrichment of either component occurs on further distillation.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): For an ideal solution of A and B, the plot of total vapour pressure versus mole fraction of B is a straight line. Reason (R): In an ideal solution, both partial vapour pressures vary linearly with mole fraction according to Raoult's law, so the total pressure is also linear.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): The van't Hoff factor i is always greater than 1 for strong electrolytes dissolved in water. Reason (R): Strong electrolytes completely dissociate in water, increasing the total number of particles in solution, which increases colligative properties.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): Acetic acid in benzene shows a van't Hoff factor of approximately 0.5. Reason (R): Acetic acid molecules undergo dimerisation in benzene through hydrogen bonding, reducing the number of solute particles to half.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 19

Logic Check

Assertion (A): Reverse osmosis can be used to purify seawater. Reason (R): When a pressure greater than the osmotic pressure is applied to the seawater side, pure water passes through the cellulose acetate membrane, leaving salts and ions behind.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): The freezing point of a solution is always lower than that of the pure solvent. Reason (R): The vapour pressure of the solution is lower than that of pure solvent. The solution freezes at a lower temperature where its vapour pressure equals that of the solid solvent.

Reasoning Options

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Chapter sections

Chapter 1: Solutions | Assertion-Reason

Assertion (A): Molality is preferred over molarity for expressing concentrations in experiments involving temperature changes. Reason (R): Molality depends on the mass of solvent, which does not change with temperature, while molarity depends on volume, which changes with temperature.

Assertion (A): The vapour pressure of a solution of a non-volatile solute is always lower than that of the pure solvent at the same temperature. Reason (R): The presence of solute molecules reduces the fraction of solvent molecules at the surface, lowering the rate of evaporation.

Assertion (A): The boiling point of a solution is always higher than that of the pure solvent. Reason (R): The vapour pressure of a solution is lower than that of the pure solvent; therefore, a higher temperature is needed to make the vapour pressure equal to atmospheric pressure.

Assertion (A): Soft drink bottles are sealed under high pressure of CO₂. Reason (R): According to Henry's law, the solubility of CO₂ in water increases with increasing pressure, keeping more CO₂ dissolved in the drink.

Assertion (A): Aquatic animals are more comfortable in cold water than in warm water. Reason (R): The solubility of oxygen in water is higher at lower temperatures because dissolution of gases is an exothermic process.

Assertion (A): The sum of mole fractions of all components in a solution is always equal to unity. Reason (R): Mole fraction of each component is defined as the ratio of its moles to the total moles of all components in the solution.

Assertion (A): The relative lowering of vapour pressure is a colligative property. Reason (R): Relative lowering of vapour pressure depends on the number of solute particles relative to solvent molecules, irrespective of the nature of solute.

Assertion (A): Ethanol-water solution shows positive deviation from Raoult's law. Reason (R): In ethanol-water mixture, the A-B (ethanol-water) interactions are stronger than A-A (ethanol-ethanol) or B-B (water-water) interactions.

Assertion (A): The experimentally determined molar mass of KCl in water is lower than its true molar mass. Reason (R): KCl dissociates into K⁺ and Cl⁻ in water, increasing the number of particles in solution, which increases colligative properties, leading to a lower calculated molar mass.

Assertion (A): Pressure has no significant effect on the solubility of solids in liquids. Reason (R): Solids and liquids are nearly incompressible; their volumes (and hence solubility) remain essentially unaffected by changes in pressure.

Assertion (A): The component present in the largest quantity in a solution is called the solvent. Reason (R): The solvent determines the physical state in which the solution exists.

Assertion (A): Nitric acid-water mixture (68% HNO₃) forms a maximum boiling azeotrope at 393.5 K. Reason (R): HNO₃-water mixture shows large negative deviation from Raoult's law, resulting in a lower vapour pressure and hence a higher boiling point at the azeotropic composition.

Assertion (A): Solvent molecules always flow from lower concentration of solution to higher concentration during osmosis. Reason (R): Solvent molecules move from a region of higher chemical potential (pure solvent/dilute solution) to a region of lower chemical potential (concentrated solution).

Assertion (A): For an ideal solution of A and B, the plot of total vapour pressure versus mole fraction of B is a straight line. Reason (R): In an ideal solution, both partial vapour pressures vary linearly with mole fraction according to Raoult's law, so the total pressure is also linear.

Assertion (A): The van't Hoff factor i is always greater than 1 for strong electrolytes dissolved in water. Reason (R): Strong electrolytes completely dissociate in water, increasing the total number of particles in solution, which increases colligative properties.

Assertion (A): Acetic acid in benzene shows a van't Hoff factor of approximately 0.5. Reason (R): Acetic acid molecules undergo dimerisation in benzene through hydrogen bonding, reducing the number of solute particles to half.

Assertion (A): Reverse osmosis can be used to purify seawater. Reason (R): When a pressure greater than the osmotic pressure is applied to the seawater side, pure water passes through the cellulose acetate membrane, leaving salts and ions behind.

Assertion (A): The freezing point of a solution is always lower than that of the pure solvent. Reason (R): The vapour pressure of the solution is lower than that of pure solvent. The solution freezes at a lower temperature where its vapour pressure equals that of the solid solvent.

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