CBSE Class 12 Chemistry Solutions MCQs Set K

Question: Which of the following units is useful in relating concentration of solution with its vapour pressure?
a) mole fraction
b) parts per million
c) mass percentage
d) molality
Answer: a

Question: A beaker contains a solution of substance ‘A’. Precipitation occurs when a small amount of ‘A’ is added. The solution is—
a) saturated
b) supersaturated
c) unsaturated
d) concentrated
Answer: b

Question: The value of Henry’s constant KH is—
a) greater for gases with higher solubility
b) greater for gases with lower solubility
c) constant for all gases
d) not related to solubility
Answer: b

Question: Low concentration of oxygen in people at high altitude is due to—
a) low temperature
b) low atmospheric pressure
c) high atmospheric pressure
d) both low temperature and high atmospheric pressure
Answer: b

Question: Maximum amount of a solute that can be dissolved in a solvent does not depend on—
a) Temperature
b) Nature of solute
c) Pressure
d) Nature of solvent
Answer: c

Question: At equilibrium, the rate of dissolution of a solid solute in a volatile solvent is—
a) less than crystallisation
b) greater than crystallisation
c) equal to crystallisation
d) zero
Answer: c

Question: Considering hydrogen bonding, which mixture shows positive deviation from Raoult’s law?
a) Methanol and acetone
b) Chloroform and acetone
c) Nitric acid and water
d) Phenol and aniline
Answer: a

Question: On dissolving sugar in water solution feels cool. Dissolution is most rapid in—
a) Sugar crystals in cold water
b) Sugar crystals in hot water
c) Powdered sugar in cold water
d) Powdered sugar in hot water
Answer: d

Question: The values of Van’t Hoff factor for KCl, NaCl and K₂SO₄ respectively are—
a) 2, 2, 2
b) 2, 2, 3
c) 1, 1, 2
d) 1, 1, 1
Answer: b

Question: Value of Henry’s constant KH—
a) increases with temperature
b) decreases with temperature
c) remains constant
d) first increases then decreases
Answer: a

Question: An unripe mango shrivels in concentrated salt solution because—
a) it gains water by osmosis
b) it loses water by reverse osmosis
c) it gains water by reverse osmosis
d) it loses water by osmosis
Answer: d

Question: At a given temperature osmotic pressure of a concentrated solution is—
a) higher than that of a dilute solution
b) lower than that of a dilute solution
c) same as that of a dilute solution
d) cannot be compared
Answer: a

Question: Van’t Hoff factor for NaCl solutions 0.1M, 0.01M, 0.001M will be—
a) iA < iB < iC
b) iA > iB > iC
c) iA = iB = iC
d) iA < iB > iC
Answer: c

Question: Which statement is false?
a) Units of atmospheric and osmotic pressure are same
b) In reverse osmosis solvent moves from low solute concentration to high
c) Molal depression constant depends on nature of solvent
d) Relative lowering of vapour pressure is dimensionless
Answer: b

Question: Which aqueous solution has highest boiling point?
a) 1.0 M NaOH
b) 1.0 M Na₂SO₄
c) 1.0 M NH₄NO₃
d) 1.0 M KNO₃
Answer: b

Question: Depression in freezing point of 0.01 M MgCl₂ compared to 0.01 M glucose is—
a) same
b) about twice
c) about three times
d) about six times
Answer: c

Question: Minimum boiling azeotrope is formed when—
a) A–B interactions are stronger than A–A or B–B
b) vapour pressure increases as more molecules escape
c) vapour pressure decreases as fewer molecules escape
d) A–B interactions are weaker than A–A or B–B
Answer: a

Question: Colligative properties depend on—
a) nature of solute particles
b) number of solute particles
c) physical properties of solute
d) nature of solvent
Answer: b

Question: Which statement is false?
a) Two sucrose solutions of same molality in different solvents have same ΔTf
b) Osmotic pressure Π = CRT
c) Osmotic pressure order: BaCl₂ > KCl > CH₃COOH > sucrose
d) Vapour pressure ∝ mole fraction of volatile component
Answer: a

ASSERTION -REASON TYPE

A statement of assertion is followed by a statement of reason. Mark the correct choice from the options given below:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.

Question: Assertion : Osmosis does not take place in two isotonic solutions separated by semi-permeable membrane.
Reason : Isotonic solutions have same osmotic pressure.
Answer: a

Question: Assertion : Two liquids nitric acid and water form a maximum boiling azeotrope when mixed in the ratio of 68% and 32% respectively.
Reason : Interaction between nitric acid and water are stronger than nitric acid – nitric acid interactions and water – water interactions.
Answer: a

Question: Assertion : Lowering of vapour pressure is not dependent on the number of species present in the solution.
Reason : Lowering of vapour pressure and relative lowering of vapour pressure are colligative properties.
Answer: d

Question: Assertion : In an ideal solution, Δmix H is zero.
Reason : In an ideal solution, A – B interactions are lower than A-A and B-B interactions.
Answer: c

Question: Assertion : 1 M solution of KCl has greater osmotic pressure than 1 M solution of glucose at same temperature.
Reason : In solution KCl dissociates to produce more number of particles.
Answer: a

One – word answers

Question: Liquids A and B on mixing produce a warm solution. Which type of deviation from Raoult’s law is shown?
Answer. Negative deviation

Question: Liquid ‘Y’ has higher vapour pressure than liquid ’ X’ . Which of them will have higher boiling point.
Answer. X

Question: Under what condition Van’t Hoff factor is less than 1?
Answer. Association