51. If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the freezing point depression of the solution? (Cryoscopic constant of water, Kf=1.86°C⋅kg/mol)
a) 1.86°C
b) 3.72°C
c) 5.58°C
d) 0.93°C
Answer: a) 1.86°C
Explanation:
The freezing point depression is calculated using ΔTf=Kf×m
52. Which of the following solutions will have the lowest freezing point?
a) 0.1 M glucose
b) 0.1 M NaCl
c) 0.1 M K₂SO₄
d) 0.1 M urea
Answer: c) 0.1 M K₂SO₄
Explanation:
The freezing point depression depends on the number of particles in solution. K₂SO₄ dissociates into 3 ions (2 K⁺ and 1 SO₄²⁻), producing more particles than NaCl (2 ions) and glucose or urea (which do not dissociate). Therefore, 0.1 M K₂SO₄ will have the lowest freezing point.
53. In a solution that follows Raoult’s law, the vapor pressure of a solvent is:
a) Higher than in the pure solvent
b) Lower than in the pure solvent
c) Equal to that of the solute
d) Independent of the solvent’s mole fraction
Answer: b) Lower than in the pure solvent
Explanation:
According to Raoult’s law, the vapor pressure of a solvent in a solution is proportional to its mole fraction. Since the mole fraction of the solvent in a solution is always less than 1, the vapor pressure in a solution is lower than that of the pure solvent.
54. Which colligative property is most effective for determining the molar mass of polymers?
a) Boiling point elevation
b) Freezing point depression
c) Osmotic pressure
d) Vapor pressure lowering
Answer: c) Osmotic pressure
Explanation:
Osmotic pressure is the most sensitive colligative property for determining the molar mass of large molecules like polymers. Small changes in concentration lead to significant changes in osmotic pressure, making it easier to measure for high molar mass substances.
55. What is the freezing point depression if 2 mol of NaCl is dissolved in 1 kg of water? (Assume complete dissociation, i=2, Kf=1.86°C⋅kg/mol)
a) 1.86°C
b) 3.72°C
c) 7.44°C
d) 9.30°C
Answer: c) 7.44°C
Explanation:
The freezing point depression is calculated using ΔTf=i×Kf×m
56. Which of the following solutions will have the lowest vapor pressure?
a) 1 M NaCl
b) 1 M glucose
c) 1 M BaCl₂
d) 1 M urea
Answer: c) 1 M BaCl₂
Explanation:
Vapor pressure lowering depends on the number of solute particles. BaCl₂ dissociates into 3 ions (Ba²⁺ and 2 Cl⁻), producing more particles than NaCl (2 ions), glucose, and urea (which do not dissociate). Therefore, 1 M BaCl₂ will have the lowest vapor pressure.
57. Which of the following statements about ideal solutions is correct?
a) Ideal solutions show positive deviation from Raoult’s law
b) Ideal solutions follow Raoult’s law at all concentrations
c) Ideal solutions have strong intermolecular forces between solute and solvent
d) Ideal solutions exhibit changes in enthalpy upon mixing
Answer: b) Ideal solutions follow Raoult’s law at all concentrations
Explanation:
An ideal solution obeys Raoult’s law over the entire range of concentrations. The intermolecular forces between the solute and solvent are similar to those in the pure components, so there is no enthalpy change upon mixing.
58. A solution of a non-volatile solute in a volatile solvent has a vapor pressure:
a) Equal to that of the pure solvent
b) Higher than that of the pure solvent
c) Lower than that of the pure solvent
d) Equal to that of the solute
Answer: c) Lower than that of the pure solvent
Explanation:
The vapor pressure of a solution containing a non-volatile solute is lower than that of the pure solvent. This is because the non-volatile solute reduces the number of solvent molecules that can escape into the vapor phase, thus lowering the vapor pressure.
59. Which of the following can be used to calculate the van’t Hoff factor (ii)?
a) Freezing point depression
b) Boiling point elevation
c) Osmotic pressure
d) All of the above
Answer: d) All of the above
Explanation:
The van’t Hoff factor (ii) can be calculated using any colligative property, such as freezing point depression, boiling point elevation, or osmotic pressure, as all of these properties depend on the number of particles in the solution.
60. Which of the following solutions will have the highest boiling point?
a) 1 M NaCl
b) 1 M glucose
c) 1 M BaCl₂
d) 1 M urea
Answer: c) 1 M BaCl₂
Explanation:
The boiling point elevation depends on the number of particles in solution. BaCl₂ dissociates into 3 ions, producing more particles than NaCl (2 ions), glucose, and urea (which do not dissociate), resulting in a higher boiling point for the BaCl₂ solution.
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