Here’s the comprehensive preparation for 50 Assertion and Reason Questions with answers and explanations for CBSE Class 12 Chemistry Chapter 2: Solutions.
Assertion (A): Vapour pressure of a solution is lower than that
of the pure solvent.
Reason (R): Non-volatile solutes reduce the number of solvent
molecules available for evaporation.
Answer: 1
Explanation: The presence of a non-volatile solute reduces the
escaping tendency of solvent molecules, lowering vapour pressure.
Assertion (A): Azeotropes cannot be separated into pure
components by simple distillation.
Reason (R): Azeotropes have the same composition in both liquid
and vapour phases.
Answer: 1
Explanation: Azeotropes behave like a single substance and boil
at a constant temperature.
Assertion (A): Colligative properties depend only on the number
of solute particles.
Reason (R): Colligative properties are independent of the
nature of solute particles.
Answer: 1
Explanation: Properties like boiling point elevation and
freezing point depression are determined by the number, not the type, of solute
particles.
Assertion (A): Adding salt to water raises the boiling point of
water.
Reason (R): Adding salt increases the vapour pressure of water.
Answer: 3
Explanation: Salt decreases the vapour pressure, requiring a
higher temperature to reach boiling.
Assertion (A): Osmotic pressure is a colligative property.
Reason (R): Osmotic pressure depends on the concentration of
solute particles in the solution.
Answer: 1
Explanation: Osmotic pressure is proportional to the number of
solute particles in the solution.
Assertion (A): A hypertonic solution has a lower osmotic
pressure than a hypotonic solution.
Reason (R): Osmosis occurs from a hypotonic solution to a
hypertonic solution.
Answer: 4
Explanation: Hypertonic solutions have higher osmotic pressure
compared to hypotonic solutions.
Assertion (A): The depression in freezing point is directly
proportional to molality.
Reason (R): Depression in freezing point is a colligative
property.
Answer: 1
Explanation: Both statements are true; the extent of freezing
point depression depends on molality.
Assertion (A): Ethylene glycol is used as an antifreeze in
automobile radiators.
Reason (R): Ethylene glycol lowers the freezing point of water.
Answer: 1
Explanation: The presence of ethylene glycol disrupts water’s
freezing point, preventing freezing in cold conditions.
Assertion (A): NaCl exhibits higher boiling point elevation
than glucose for the same molality.
Reason (R): NaCl dissociates into ions, increasing the number
of solute particles.
Answer: 1
Explanation: NaCl produces more particles in solution due to
ionization, leading to a greater elevation.
Assertion (A): Raoult’s law is applicable to ideal solutions.
Reason (R): Ideal solutions exhibit ideal behaviour over the
entire concentration range.
Answer: 1
Explanation: Ideal solutions follow Raoult’s law as there are
no deviations in their behaviour.
Assertion (A): Non-ideal solutions show positive or negative
deviations from Raoult’s law.
Reason (R): Intermolecular forces between solute and solvent
may differ from those between pure components.
Answer: 1
Explanation: Deviations arise due to differences in
interactions compared to pure components.
Assertion (A): Methanol and water form an ideal solution.
Reason (R): Methanol and water exhibit strong hydrogen bonding.
Answer: 3
Explanation: Strong hydrogen bonding leads to deviation, making
the solution non-ideal.
Assertion (A): Molality is temperature independent.
Reason (R): Molality is defined as moles of solute per kilogram
of solvent.
Answer: 1
Explanation: Since mass does not change with temperature,
molality remains constant.
Assertion (A): Acetic acid in benzene shows abnormal molar
mass.
Reason (R): Acetic acid dimerizes in benzene due to hydrogen
bonding.
Answer: 1
Explanation: Dimerization leads to a higher effective molar
mass.
Assertion (A): Solutions with higher boiling points have higher
vapour pressures.
Reason (R): The boiling point is inversely proportional to
vapour pressure.
Answer: 4
Explanation: Higher boiling points indicate lower vapour
pressures, contradicting the assertion.
Assertion (A): Boiling point elevation is a colligative
property.
Reason (R): Boiling point elevation depends on the nature of
the solute.
Answer: 3
Explanation: Boiling point elevation depends only on the number
of solute particles, not their nature.
Assertion (A): Glucose does not show any abnormal colligative
property in aqueous solutions.
Reason (R): Glucose does not dissociate or associate in water.
Answer: 1
Explanation: Glucose remains as individual molecules in water,
so it behaves normally in colligative properties.
Assertion (A): When a solute is added to a solvent, its
freezing point decreases.
Reason (R): Solute particles disrupt the formation of the solid
lattice of the solvent.
Answer: 1
Explanation: The presence of solute interferes with lattice
formation, lowering the freezing point.
Assertion (A): Raoult’s law states that the partial pressure of
a component in a solution is directly proportional to its mole fraction.
Reason (R): Mole fraction is the ratio of the number of moles
of the component to the total number of moles in the solution.
Answer: 1
Explanation: Both statements are true and describe the
relationship in Raoult’s law.
Assertion (A): The osmotic pressure of a solution decreases
with increasing temperature.
Reason (R): Osmotic pressure is inversely proportional to
temperature.
Answer: 4
Explanation: Osmotic pressure increases with temperature as it
is directly proportional to temperature (π = CRT).
Assertion (A): Ethanol and acetone form a solution with
negative deviation from Raoult’s law.
Reason (R): Strong hydrogen bonding exists between ethanol and
acetone molecules.
Answer: 3
Explanation: Ethanol and acetone exhibit positive deviation due
to weaker intermolecular forces between different molecules.
Assertion (A): Ideal solutions have an enthalpy of mixing equal
to zero.
Reason (R): In ideal solutions, intermolecular forces between
components are equal.
Answer: 1
Explanation: The equality of forces ensures no heat is absorbed
or released during mixing.
Assertion (A): Molality is a better unit than molarity for
expressing concentration in temperature-varying systems.
Reason (R): Molality depends on the mass of solvent, which
remains constant with temperature.
Answer: 1
Explanation: Molarity changes with temperature due to volume
expansion, making molality more reliable.
Assertion (A): The lowering of vapour pressure is a colligative
property.
Reason (R): Lowering of vapour pressure depends only on the
number of solute particles.
Answer: 1
Explanation: Both statements are correct and describe the
fundamental nature of colligative properties.
Assertion (A): NaCl solution freezes at a lower temperature
than pure water.
Reason (R): NaCl dissociates into ions, increasing the effect
on freezing point depression.
Answer: 1
Explanation: Dissociation of NaCl results in more particles,
enhancing the freezing point depression.
Assertion (A): Vapour pressure of a liquid decreases with the
addition of a non-volatile solute.
Reason (R): The number of solvent molecules at the surface
decreases.
Answer: 1
Explanation: Non-volatile solutes reduce the fraction of
solvent molecules that can escape into vapour.
Assertion (A): Isotonic solutions have the same osmotic
pressure.
Reason (R): Osmotic pressure depends on the concentration of
solute particles.
Answer: 1
Explanation: Solutions with equal solute particle
concentrations exhibit the same osmotic pressure.
Assertion (A): Molality is preferred over molarity for studying
colligative properties.
Reason (R): Molality remains unaffected by temperature changes.
Answer: 1
Explanation: Molality is temperature-independent as it is based
on mass, not volume.
Assertion (A): The solubility of gases in liquids decreases
with increasing temperature.
Reason (R): Higher temperatures increase the kinetic energy of
gas molecules.
Answer: 1
Explanation: Increased kinetic energy helps gas molecules
escape from the liquid, reducing solubility.
Assertion (A): Electrolytes have a greater effect on
colligative properties than non-electrolytes.
Reason (R): Electrolytes dissociate into ions, increasing the
number of solute particles.
Answer: 1
Explanation: Dissociation enhances the effective concentration,
magnifying colligative effects.
Assertion (A): Freezing point depression is inversely
proportional to molar mass of the solute.
Reason (R): Lower molar mass implies a higher number of
particles per unit mass.
Answer: 1
Explanation: Smaller molar mass solutes create more particles,
leading to greater freezing point depression.
Assertion (A): Elevation in boiling point is more for a 1 m KCl
solution than a 1 m glucose solution.
Reason (R): KCl dissociates into two ions, while glucose does
not dissociate.
Answer: 1
Explanation: KCl dissociates into two particles, doubling the
effective molality.
Assertion (A): Non-volatile solutes affect only the physical
properties of solvents.
Reason (R): Non-volatile solutes do not interact chemically
with the solvent.
Answer: 1
Explanation: Colligative properties result from physical
interaction, not chemical reactions.
Assertion (A): Colligative properties are more prominent in
electrolytic solutions.
Reason (R): Electrolytes dissociate into multiple ions.
Answer: 1
Explanation: The dissociation increases the effective number of
particles, amplifying colligative effects.
Assertion (A): A solution of 1 m glucose and 1 m urea have the
same osmotic pressure.
Reason (R): Both are non-electrolytes and have the same
particle concentration.
Answer: 1
Explanation: Since both solutions produce the same number of
particles, their osmotic pressures are identical.
Assertion (A): Sea water freezes at a temperature below 0°C.
Reason (R): Sea water contains dissolved salts that lower its
freezing point.
Answer: 1
Explanation: Dissolved salts cause freezing point depression,
preventing freezing at 0°C.
Assertion (A): Henry’s law constant for CO₂ increases with
temperature.
Reason (R): Solubility of gases in liquids decreases with
temperature.
Answer: 1
Explanation: Henry’s law constant reflects the inverse
relationship between solubility and temperature.
Assertion (A): In non-ideal solutions, the vapour pressure may
be higher or lower than expected.
Reason (R): Non-ideal solutions show deviations from Raoult’s
law.
Answer: 1
Explanation: Deviations arise from differences in
intermolecular interactions.
Assertion (A): All ionic compounds dissociate completely in
aqueous solutions.
Reason (R): Ionic compounds are highly soluble in water.
Answer: 4
Explanation: Not all ionic compounds dissociate completely;
solubility varies with the compound.
Assertion (A): The elevation in boiling point is independent of
atmospheric pressure.
Reason (R): Boiling point is defined relative to atmospheric
pressure.
Answer: 3
Explanation: Elevation in boiling point is influenced by
external pressure.
Assertion (A): Antifreeze solutions are added to car radiators
in winter.
Reason (R): Antifreeze solutions lower the freezing point of
water.
Answer: 1
Explanation: The solute (antifreeze) reduces the freezing point
of water, preventing it from freezing in cold conditions.
Assertion (A): Solutions showing positive deviation from
Raoult's law have weaker intermolecular forces between different components.
Reason (R): Components escape easily into the vapour phase due
to weaker interactions.
Answer: 1
Explanation: Positive deviation occurs when components have
weaker intermolecular forces than the pure components.
Assertion (A): The addition of salt to water increases its
boiling point.
Reason (R): Salt increases the number of solute particles,
which raises the boiling point.
Answer: 1
Explanation: Salt creates a boiling point elevation due to
increased solute particle concentration.
Assertion (A): Non-ideal solutions may show negative deviations
from Raoult's law.
Reason (R): Stronger interactions between different components
reduce vapour pressure.
Answer: 1
Explanation: Negative deviation occurs when components form
stronger bonds, lowering vapour pressure.
Assertion (A): Osmosis is the flow of solvent through a
semipermeable membrane.
Reason (R): Solvent molecules move from a region of higher
concentration to lower concentration.
Answer: 2
Explanation: Solvent moves from higher solvent concentration
(low solute) to lower solvent concentration (high solute).
Assertion (A): Colligative properties depend only on the number
of particles in a solution.
Reason (R): Colligative properties are independent of the
nature of the solute.
Answer: 1
Explanation: Both statements define the characteristics of
colligative properties.
Assertion (A): Vapour pressure of a liquid increases with an
increase in temperature.
Reason (R): At higher temperatures, more molecules have enough
energy to escape into the vapour phase.
Answer: 1
Explanation: The relationship between temperature and vapour
pressure is due to increased molecular kinetic energy.
Assertion (A): Isotonic solutions have the same osmotic
pressure but may have different solute compositions.
Reason (R): Osmotic pressure depends on the number of particles
and not their identity.
Answer: 1
Explanation: Isotonic solutions have equal osmotic pressures,
regardless of solute identity.
Assertion (A): Sugar solution shows no conductivity.
Reason (R): Sugar molecules do not dissociate into ions in
water.
Answer: 1
Explanation: Non-electrolytes like sugar do not produce ions,
so they do not conduct electricity.
Assertion (A): The osmotic pressure of a 1 M NaCl solution is
greater than that of a 1 M urea solution.
Reason (R): NaCl dissociates into two ions, whereas urea does
not dissociate.
Answer: 1
Explanation: The dissociation of NaCl produces more particles,
increasing the osmotic pressure.