Class 12 Chemistry Chapter 1 Solutions MCQs Updated 2025

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Class 12 Chemistry – Chapter 1: Solutions (MCQs)

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Q.1
Which of the following is a colligative property?
(a)Vapour pressure of solvent
(b)Relative lowering of vapour pressure
(c)Viscosity
(d)Surface tension

Answer: (b) Relative lowering of vapour pressure

Explanation: Colligative properties depend only on particle number (not nature). Relative lowering of vapour pressure is one such property.

Q.2
Elevation in boiling point (ΔTb) is directly proportional to:
(a)Mole fraction of solvent
(b)Vapour pressure of solution
(c)Molality of the solution
(d)Molarity of the solution

Answer: (c) Molality of the solution

Explanation: ΔTb = Kb·m where m is molality.

Q.3
For a non-volatile solute in a volatile solvent, Raoult’s law states that the relative lowering of vapour pressure equals the:
(a)Mole fraction of solvent
(b)Mole fraction of solute
(c)Molality of solute
(d)Molarity of solute

Answer: (b) Mole fraction of solute

Explanation: (p0 − p)/p0 = xsolute.

Q.4
The unit of molality is:
(a)mol L−1
(b)mol kg−1
(c)g L−1
(d)% (w/v)

Answer: (b) mol kg−1

Explanation: Molality is moles of solute per kilogram of solvent.

Q.5
The van’t Hoff factor i accounts for:
(a)Solvent–solvent interactions
(b)Association/dissociation of solute
(c)Change in volume of solution
(d)Temperature dependence of Kb

Answer: (b) Association/dissociation of solute

Explanation: i modifies colligative formulas to match the effective particle count.

Q.6
For an ideal binary solution of volatile liquids A and B, the total vapour pressure is given by:
(a)p = xApA0
(b)p = xBpB0
(c)p = xApA0 + xBpB0
(d)p = pA0 + pB0

Answer: (c) p = xApA0 + xBpB0

Explanation: Raoult’s law for both components with xA + xB = 1.

Q.7
Osmotic pressure is measured using:
(a)Manometer
(b)Osmometer
(c)Polarimeter
(d)Calorimeter

Answer: (b) Osmometer

Explanation: Osmometers determine π using semipermeable membranes.

Q.8
For a dilute solution, osmotic pressure (π) at temperature T is given by:
(a)π = Kb·m
(b)π = CRT
(c)π = iKf·m
(d)π = p/p0

Answer: (b) π = CRT

Explanation: C is molar concentration; analogous to ideal gas law.

Q.9
Depression in freezing point is used to determine:
(a)Molar mass of solute
(b)Mole fraction of solvent
(c)Density of solution
(d)Osmotic coefficient

Answer: (a) Molar mass of solute

Explanation: ΔTf = Kf·m allows calculation of molar mass.

Q.10
Henry’s law constant for a gas increases with temperature. Solubility of the gas in liquid will:
(a)Increase
(b)Decrease
(c)Remain same
(d)First increase then decrease

Answer: (b) Decrease

Explanation: Higher KH means lower solubility (p = KHx).

Q.11
In a solution showing positive deviation from Raoult’s law, intermolecular interactions are:
(a)Stronger than pure components
(b)Weaker than pure components
(c)Same as pure components
(d)Unpredictable

Answer: (b) Weaker than pure components

Explanation: Leads to higher vapour pressure than ideal.

Q.12
The cryoscopic constant Kf depends on the:
(a)Nature of solute
(b)Nature of solvent
(c)Both solute and solvent
(d)Temperature only

Answer: (b) Nature of solvent

Explanation: Kf and Kb are solvent properties.

Q.13
Which concentration unit is temperature independent?
(a)Molarity
(b)Molality
(c)% (w/v)
(d)Normality

Answer: (b) Molality

Explanation: Based on mass of solvent, not volume.

Q.14
If a solute dimerises in solution, the observed van’t Hoff factor will be:
(a)> 1
(b)= 1
(c)< 1
(d)Unchanged

Answer: (c) < 1

Explanation: Association reduces particle number.

Q.15
Which statement is true for an electrolyte solution (ideal dilution)?
(a)i = 1 always
(b)i < 1 due to association
(c)i > 1 due to dissociation
(d)i depends only on temperature

Answer: (c) i > 1 due to dissociation

Explanation: Electrolytes produce more particles than formula units.

Q.16
Which pair is most likely to form an ideal solution?
(a)Acetone + Chloroform
(b)Benzene + Toluene
(c)Ethanol + Water
(d)Acetone + Water

Answer: (b) Benzene + Toluene

Explanation: Similar size and intermolecular forces → near-ideal behavior.

Q.17
Colligative properties are not useful when solute:
(a)Is non-volatile and non-electrolyte
(b)Associates or dissociates in solution
(c)Is large molar mass
(d)Is sparingly soluble

Answer: (b) Associates or dissociates in solution

Explanation: Particle number changes; need van’t Hoff factor correction.

Q.18
Which statement is correct about azeotropes?
(a)They obey Raoult’s law at all compositions
(b)They cannot be separated by simple distillation
(c)They are pure compounds
(d)They have zero vapour pressure

Answer: (b) They cannot be separated by simple distillation

Explanation: Constant boiling mixtures boil without change in composition.

Q.19
Which is true for a solution showing negative deviation from Raoult’s law?
(a)ptotal > pideal
(b)Intermolecular attractions are stronger
(c)Endothermic mixing
(d)Higher vapour pressure

Answer: (b) Intermolecular attractions are stronger

Explanation: ptotal < pideal; exothermic mixing.

Q.20
Which combination gives maximum elevation in boiling point for the same mass of solute added?
(a)Lowest molar mass, non-electrolyte
(b)High molar mass, non-electrolyte
(c)High molar mass, electrolyte (i small)
(d)Lowest molar mass, strong electrolyte

Answer: (d) Lowest molar mass, strong electrolyte

Explanation: More particles per gram (low M) and dissociation (higher i) → larger ΔTb.

Q.1: Which of the following is a colligative property?
(a) Boiling point
(b) Osmotic pressure
(c) Viscosity
(d) Surface tension

Answer: (b) Osmotic pressure
Explanation: Colligative properties depend on the number of solute particles in a solution, not on the nature of the solute. Osmotic pressure is one such property.

Q.2: The molality of a solution containing 18g of glucose (C₆H₁₂O₆) in 500g of water is:
(a) 0.1 m
(b) 0.2 m
(c) 0.5 m
(d) 1.0 m

Answer: (b) 0.2 m
Explanation: Molality (m) = moles of solute / mass of solvent (kg). Moles of glucose = 18/180 = 0.1 moles. Molality = 0.1 moles / 0.5 kg = 0.2 m.

Q.3: Raoult’s Law is applicable to:
(a) Non-ideal solutions
(b) Dilute solutions
(c) Ideal solutions
(d) Concentrated solutions

Answer: (c) Ideal solutions
Explanation: Raoult's Law states that the partial vapor pressure of each volatile component in an ideal solution is directly proportional to its mole fraction.

Q.4: Which of the following statements is true for an ideal solution?
(a) ΔHmix = 0
(b) ΔVmix ≠ 0
(c) ΔHmix ≠ 0
(d) ΔVmix ≠ 0

Answer: (a) ΔH_mix = 0
Explanation: For an ideal solution, the enthalpy change of mixing (ΔH_mix) is zero because the intermolecular forces between the molecules of the solute and solvent are similar to those in the pure components.

Q.5: The boiling point of a solution increases if:
(a) Solute is non-volatile
(b) Solute is volatile
(c) Pressure is decreased
(d) None of the above

Answer: (a) Solute is non-volatile
Explanation: Boiling point elevation occurs when a non-volatile solute is added to a solvent, increasing the boiling point of the solution compared to the pure solvent.

Q.6: Which of the following expresses Henry’s Law?
(a) P = k_H * x
(b) P = k_H / x
(c) P = x / k_H
(d) P = k_H + x

Answer: (a) P = k_H * x
Explanation: Henry's Law states that the partial pressure of a gas in a liquid is directly proportional to the mole fraction of the gas in the liquid, where k_H is Henry's constant.

Q.7: The term used to describe the lowering of vapor pressure in a solution is:
(a) Relative lowering of vapor pressure
(b) Absolute lowering of vapor pressure
(c) Osmotic pressure
(d) Elevation of boiling point

Answer: (a) Relative lowering of vapor pressure
Explanation: Relative lowering of vapor pressure is the ratio of the lowering of vapor pressure to the vapor pressure of the pure solvent, which is a colligative property.

Q.8: Which among the following is a suitable example of a colloidal solution?
(a) Salt in water
(b) Sugar in water
(c) Milk
(d) Benzene in water

Answer: (c) Milk
Explanation: Milk is an example of a colloidal solution where fat globules are dispersed in water.

Q.9: When a non-volatile solute is added to a solvent, the vapor pressure of the solvent:
(a) Increases
(b) Decreases
(c) Remains the same
(d) None of the above

Answer: (b) Decreases
Explanation: The addition of a non-volatile solute decreases the vapor pressure of the solvent because the solute particles occupy space at the surface, reducing the number of solvent molecules that can escape into the vapor phase.

Q.10: The process of separation of solute particles from a solvent using a semi-permeable membrane is known as:
(a) Diffusion
(b) Osmosis
(c) Dialysis
(d) Filtration

Answer: (b) Osmosis
Explanation: Osmosis is the process in which solvent molecules move through a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Q.11: Which of the following can show positive deviation from Raoult’s law?
(a) Ethanol and water
(b) Acetone and chloroform
(c) Benzene and toluene
(d) n-Hexane and n-Heptane

Answer: (a) Ethanol and water
Explanation: Positive deviation from Raoult's law occurs when the intermolecular forces between the solute and solvent are weaker than those between the molecules of the pure components, as seen in the ethanol-water mixture.

Q.12: The freezing point of a solution is:
(a) Higher than the freezing point of the pure solvent
(b) Lower than the freezing point of the pure solvent
(c) Equal to the freezing point of the pure solvent
(d) None of the above

Answer: (b) Lower than the freezing point of the pure solvent
Explanation: Freezing point depression occurs when a solute is added to a solvent, causing the freezing point of the solution to be lower than that of the pure solvent.

Q.13: Which factor does not affect the solubility of a solid in a liquid?
(a) Temperature
(b) Pressure
(c) Nature of the solute and solvent
(d) Concentration

Answer: (d) Concentration
Explanation: The solubility of a solid in a liquid is influenced by temperature, pressure (in the case of gases), and the nature of the solute and solvent, but not by the concentration of the solution.

Q.14: A solution has a concentration of 1 ppm. This means:
(a) 1 g of solute in 1 L of solution
(b) 1 mg of solute in 1 L of solution
(c) 1 g of solute in 1 kg of solution
(d) 1 mg of solute in 1 kg of solution

Answer: (b) 1 mg of solute in 1 L of solution
Explanation: 1 ppm (part per million) corresponds to 1 milligram of solute in 1 liter of solution.

Q.15: Which of the following is not a method to express the concentration of a solution?
(a) Molality
(b) Molarity
(c) Normality
(d) Fluidity

Answer: (d) Fluidity
Explanation: Molality, molarity, and normality are all methods to express the concentration of a solution, whereas fluidity is a measure of a liquid's flow characteristics.

Q.16: The process by which molecules of a solvent pass through a semi-permeable membrane from a dilute solution to a concentrated solution is called:
(a) Diffusion
(b) Osmosis
(c) Dialysis
(d) Filtration

Answer: (b) Osmosis
Explanation: Osmosis is the process where solvent molecules move from a region of lower solute concentration to a region of higher solute concentration through a semi-permeable membrane.

Q.17: The addition of which of the following will not change the boiling point of water?
(a) NaCl
(b) C₂H₅OH
(c) CH₃OH
(d) H₂

Answer: (d) H₂
Explanation: H₂ (hydrogen gas) does not dissolve significantly in water and hence will not affect its boiling point, unlike NaCl, C₂H₅OH, and CH₃OH which do.

Q.18: The van’t Hoff factor (i) for a dilute solution of K₄[Fe(CN)₆] is:
(a) 1
(b) 2
(c) 4
(d) 5

Answer: (d) 5
Explanation: K₄[Fe(CN)₆] dissociates into 4 K⁺ ions and 1 [Fe(CN)₆]⁴⁻ ion, giving a total of 5 particles in solution. Therefore, the van't Hoff factor (i) is 5.

Q.19: Which of the following solutions will have the highest boiling point?
(a) 1 M NaCl
(b) 1 M glucose
(c) 1 M sucrose
(d) 1 M urea

Answer: (a) 1 M NaCl
Explanation: NaCl dissociates into two ions (Na⁺ and Cl⁻) in solution, increasing the number of particles and hence the boiling point more than the non-electrolytes (glucose, sucrose, urea) which do not dissociate.

Q.20: The colligative property used to determine the molar mass of a solute is:
(a) Viscosity
(b) Surface tension
(c) Depression in freezing point
(d) Refractive index

Answer: (c) Depression in freezing point
Explanation: Depression in freezing point, a colligative property, is used to determine the molar mass of a solute by measuring the extent to which the freezing point of the solvent is lowered.

Q.21: The process of separating colloidal particles from impurities by means of diffusion through a semi-permeable membrane is called:
(a) Dialysis
(b) Osmosis
(c) Diffusion
(d) Filtration

Answer: (a) Dialysis Explanation: Dialysis is used to separate colloidal particles from smaller impurities by allowing only the smaller particles to pass through a semi-permeable membrane.

Q.22: Which of the following substances will show minimum elevation in boiling point when dissolved in 1 kg of water?
(a) NaCl
(b) Urea
(c) K₂SO₄
(d) Glucose

Answer: (b) Urea Explanation: Urea does not ionize and provides only one particle per molecule, resulting in a smaller elevation in boiling point compared to NaCl and K₂SO₄ which ionize to produce more particles.

Q.23: For a given solvent, the boiling point of a solution is always:
(a) Higher than that of the pure solvent
(b) Lower than that of the pure solvent
(c) Same as that of the pure solvent
(d) None of the above

Answer: (a) Higher than that of the pure solvent Explanation: The presence of a solute in a solvent elevates the boiling point of the solution compared to the pure solvent.

Q.24: Which of the following statements is correct regarding a 0.1 M NaCl solution and a 0.1 M glucose solution?
(a) Both will have the same osmotic pressure
(b) NaCl solution will have higher osmotic pressure
(c) Glucose solution will have higher osmotic pressure
(d) Both will have the same boiling point

Answer: (b) NaCl solution will have higher osmotic pressure Explanation: NaCl dissociates into two ions, increasing the number of solute particles and thereby the osmotic pressure compared to glucose which does not dissociate.

Q.25: The molality of a solution in which 0.5 mole of solute is dissolved in 250g of solvent is:
(a) 1 m
(b) 2 m
(c) 0.5 m
(d) 4 m

Answer: (b) 2 m Explanation: Molality (m) = moles of solute / mass of solvent (kg). Molality = 0.5 moles / 0.25 kg = 2 m.

Q.26: The freezing point of a solution is affected by:
(a) The nature of the solute
(b) The amount of solute
(c) The nature of the solvent
(d) All of the above

Answer: (d) All of the above Explanation: The freezing point of a solution depends on the nature of the solute, the amount of solute, and the nature of the solvent.

Q.27: Which of the following has the highest van’t Hoff factor (i)?
(a) KCl
(b) Na₂SO₄
(c) BaCl₂
(d) Glucose

Answer: (b) Na₂SO₄ Explanation: Na₂SO₄ dissociates into three ions (2 Na⁺ and 1 SO₄²⁻), giving a van't Hoff factor of 3, which is higher than that of KCl (2), BaCl₂ (3), and glucose (1, as it does not dissociate).

Q.28: Which of the following statements is not true for ideal solutions?
(a) They follow Raoult’s law over the entire range of concentration
(b) ΔH_mix = 0
(c) ΔV_mix = 0
(d) They are formed only by non-polar solvents

Answer: (d) They are formed only by non-polar solvents Explanation: Ideal solutions can be formed by both polar and non-polar solvents as long as the intermolecular forces between the solute and solvent molecules are similar to those in the pure components.

Q.29: The solubility of gases in liquids decreases with:
(a) Increase in pressure
(b) Increase in temperature
(c) Increase in concentration
(d) Decrease in temperature

Answer: (b) Increase in temperature Explanation: The solubility of gases in liquids generally decreases with an increase in temperature because gas molecules gain kinetic energy and escape from the solvent.

Q.30: Which of the following solutions shows a negative deviation from Raoult’s law?
(a) Ethanol and acetone
(b) Benzene and toluene
(c) Chloroform and acetone
(d) Hexane and heptane

Answer: (c) Chloroform and acetone Explanation: Negative deviation from Raoult's law occurs when the intermolecular forces between solute and solvent molecules are stronger than those in the pure components, as seen in chloroform and acetone.

Q.31: The osmotic pressure of a solution increases with:
(a) Decrease in temperature
(b) Increase in temperature
(c) Increase in the number of solute particles
(d) Both (b) and (c)

Answer: (d) Both (b) and (c) Explanation: Osmotic pressure is directly proportional to the number of solute particles and the temperature of the solution.

Q.32: The ebullioscopic constant (Kb) depends on:
(a) Nature of the solute
(b) Nature of the solvent
(c) Temperature
(d) Both (a) and (b)

Answer: (b) Nature of the solvent Explanation: The ebullioscopic constant (K_b) is a property of the solvent and does not depend on the solute.

Q.33: The depression in freezing point is directly proportional to:
(a) The molarity of the solution
(b) The molality of the solution
(c) The normality of the solution
(d) The volume of the solution

Answer: (b) The molality of the solution Explanation: Depression in freezing point is a colligative property that is directly proportional to the molality of the solution.

Q.34: The boiling point of a liquid is the temperature at which its vapor pressure is equal to:
(a) 1 atm
(b) 1 torr
(c) The external pressure
(d) The atmospheric pressure

Answer: (c) The external pressure Explanation: The boiling point of a liquid is defined as the temperature at which its vapor pressure equals the external pressure applied to it.

Q.35: The phenomenon of osmosis is due to:
(a) Diffusion of solute particles
(b) Diffusion of solvent particles
(c) Movement of solute particles against a concentration gradient
(d) None of the above

Answer: (b) Diffusion of solvent particles Explanation: Osmosis is the movement of solvent particles through a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Q.36: An azeotropic mixture of two liquids has a boiling point:
(a) Higher than either of the pure components
(b) Lower than either of the pure components
(c) Same as the boiling point of the pure component with the lower boiling point
(d) Same as the boiling point of the pure component with the higher boiling point

Answer: (a) Higher than either of the pure components Explanation: An azeotropic mixture has a constant boiling point that can be higher or lower than the boiling points of the individual components, but when it shows a positive deviation, it is higher than the boiling point of either pure component.

Q.37: The term ‘isotonic solutions’ refers to:
(a) Solutions with the same concentration of solute
(b) Solutions with the same osmotic pressure
(c) Solutions with the same boiling point
(d) Solutions with the same freezing point

Answer: (b) Solutions with the same osmotic pressure Explanation: Isotonic solutions have the same osmotic pressure, meaning they have equal concentrations of solute particles.

Q.38: Which of the following has the highest value of i (van’t Hoff factor)?
(a) NaCl
(b) K₂SO₄
(c) Al₂(SO₄)₃
(d) C₆H₁₂O₆

Answer: (c) Al₂(SO₄)₃ Explanation: Al₂(SO₄)₃ dissociates into 5 ions (2 Al³⁺ and 3 SO₄²⁻), resulting in the highest van't Hoff factor (i = 5) compared to NaCl (2), K₂SO₄ (3), and C₆H₁₂O₆ (1).

Q.39: Which of the following is a non-volatile solute?
(a) NaCl
(b) C₂H₅OH
(c) CH₃COOH
(d) CO₂

Answer: (a) NaCl Explanation: NaCl is a non-volatile solute, meaning it does not evaporate easily and thus increases the boiling point of the solvent.

Q.40: Which of the following statements is incorrect?
(a) The boiling point of a solution is always higher than that of the pure solvent
(b) The freezing point of a solution is always lower than that of the pure solvent
(c) The vapor pressure of a solution is higher than that of the pure solvent
(d) The osmotic pressure of a solution is higher than that of the pure solvent

Answer: (c) The vapor pressure of a solution is higher than that of the pure solvent Explanation: The vapor pressure of a solution is lower than that of the pure solvent due to the presence of non-volatile solute particles which lower the escaping tendency of solvent molecules.

Q.41: Henry’s law constant (kH) is dependent on:
(a) Temperature
(b) Pressure
(c) Nature of the gas
(d) Both (a) and (c)

Answer: (d) Both (a) and (c) Explanation: Henry's law constant (k_H) is dependent on the temperature and the nature of the gas.

Q.42: A solution containing 10g of solute in 100g of solvent is referred to as:
(a) 10% (w/w) solution
(b) 10% (v/v) solution
(c) 10 ppm solution
(d) 10 molal solution

Answer: (a) 10% (w/w) solution Explanation: A 10% (w/w) solution means 10g of solute is dissolved in 100g of solvent.

Q.43: The addition of a non-volatile solute to a solvent results in:
(a) Increase in vapor pressure
(b) Decrease in boiling point
(c) Decrease in freezing point
(d) Decrease in osmotic pressure

Answer: (c) Decrease in freezing point Explanation: The addition of a non-volatile solute lowers the freezing point of the solvent, a phenomenon known as freezing point depression.

Q.44: The unit of molality is:
(a) mol/L
(b) mol/kg
(c) mol/g
(d) mol/m³

Answer: (b) mol/kg Explanation: Molality is expressed in moles of solute per kilogram of solvent (mol/kg).

Q.45: The van’t Hoff factor (i) for a dilute solution of AlCl₃ is:
(a) 1
(b) 2
(c) 3
(d) 4

Answer: (d) 4 Explanation: AlCl₃ dissociates into 4 ions (1 Al³⁺ and 3 Cl⁻), giving a van't Hoff factor (i) of 4.

Q.46: Colligative properties depend on:
(a) The nature of solute particles
(b) The number of solute particles
(c) The chemical identity of the solute
(d) The physical state of the solute

Answer: (b) The number of solute particles Explanation: Colligative properties are dependent on the number of solute particles present in a solution, not their nature.

Q.47: Which of the following solutions is not an example of a colloid?
(a) Milk
(b) Butter
(c) Salt in water
(d) Smoke

Answer: (c) Salt in water Explanation: Salt in water is a true solution, not a colloid. Colloids have larger dispersed particles, such as those in milk, butter, and smoke.

Q.48: The concentration term that is temperature-independent is:
(a) Molarity
(b) Molality
(c) Normality
(d) Volume percentage

Answer: (b) Molality Explanation: Molality is temperature-independent as it is based on the mass of the solvent, which does not change with temperature.

Q.49: Which of the following will not change the vapor pressure of a solution?
(a) Changing the amount of solute
(b) Changing the nature of the solute
(c) Changing the temperature
(d) Changing the solvent

Answer: (b) Changing the nature of the solute Explanation: Vapor pressure depends on the number of solute particles and temperature, not the chemical nature of the solute.

Q.50: The freezing point of 1 molal solution of a non-electrolyte in water is:
(a) 0°C
(b) -1.86°C
(c) -3.72°C
(d) 100°C

Answer: (b) -1.86°C Explanation: The freezing point depression constant (K_f) for water is 1.86°C kg/mol. Thus, a 1 molal solution of a non-electrolyte will lower the freezing point by 1.86°C.

Q.51: The term ‘colligative properties’ refers to properties that:
(a) Depend on the chemical nature of the solute
(b) Depend on the number of solute particles
(c) Depend on the physical state of the solute
(d) Depend on the volume of the solvent

Answer: (b) Depend on the number of solute particles Explanation: Colligative properties depend on the number of solute particles in a solution, regardless of their chemical nature.

Q.52: The ratio of the number of moles of solute to the mass of solvent in kg is called:
(a) Molarity
(b) Molality
(c) Normality
(d) Volume percentage

Answer: (b) Molality Explanation: Molality is defined as the number of moles of solute per kilogram of solvent.

Q.53: The vapor pressure of a solution is lower than that of the pure solvent because:
(a) Solute particles attract solvent particles
(b) Solute particles repel solvent particles
(c) Solute particles occupy space
(d) None of the above

Answer: (a) Solute particles attract solvent particles Explanation: Solute particles attract solvent particles, reducing their ability to escape into the vapor phase, thereby lowering the vapor pressure.

Q.54: The solubility of a gas in a liquid at constant temperature is directly proportional to:
(a) The volume of the gas
(b) The pressure of the gas
(c) The temperature of the gas
(d) The nature of the gas

Answer: (b) The pressure of the gas Explanation: According to Henry's law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.

Q.55: Which one of the following statements about Raoult’s law is not correct?
(a) It is applicable to ideal solutions
(b) It relates vapor pressure of a solution to the mole fraction of the solvent
(c) It is valid over a wide range of concentrations
(d) It is not applicable to non-ideal solutions

Answer: (c) It is valid over a wide range of concentrations Explanation: Raoult's law is only strictly applicable to ideal solutions and is most accurate at low concentrations of solute.

Q.56: In a solution of two liquids, A and B, if the partial vapor pressure of A is higher than expected from Raoult’s law, the solution exhibits:
(a) Positive deviation
(b) Negative deviation
(c) No deviation
(d) Ideal behavior

Answer: (a) Positive deviation Explanation: Positive deviation occurs when the intermolecular forces between unlike molecules are weaker than those between like molecules, resulting in higher vapor pressures.

Q.57: When the freezing point of a solvent is lowered upon the addition of a non-volatile solute, it is called:
(a) Boiling point elevation
(b) Freezing point depression
(c) Vapor pressure lowering
(d) Osmotic pressure

Answer: (b) Freezing point depression Explanation: Freezing point depression refers to the decrease in the freezing point of a solvent due to the addition of a non-volatile solute.

Q.58: Which one of the following does not affect the colligative properties of a solution?
(a) Nature of the solute
(b) Number of solute particles
(c) Concentration of solute particles
(d) Temperature

Answer: (a) Nature of the solute Explanation: Colligative properties depend on the number and concentration of solute particles, not their chemical nature.

Q.59: A 0.1 M solution of which of the following substances will have the highest boiling point?
(a) NaCl
(b) KNO₃
(c) MgCl₂
(d) C₆H₁₂O₆

Answer: (c) MgCl₂ Explanation: MgCl₂ dissociates into three ions (1 Mg²⁺ and 2 Cl⁻), giving a higher elevation in boiling point compared to NaCl (2 ions), KNO₃ (2 ions), and C₆H₁₂O₆ (non-electrolyte).

Q.60: The presence of which of the following will not affect the freezing point of water?
(a) NaCl
(b) Urea
(c) Ethanol
(d) Water

Answer: (d) Water Explanation: Adding more water to water does not affect its freezing point, whereas solutes like NaCl, urea, and ethanol will lower the freezing point.

✍🏻More MCQs from Class 12 Chemistry📓

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