71. The van’t Hoff factor (i) is related to:
A. The degree of dissociation or association of solute particles
B. The molecular weight of solute particles
C. The solubility of the solute
D. The volume of the solvent
Answer: A. The degree of dissociation or association of solute particles
Explanation:
The van’t Hoff factor (i) accounts for the number of particles formed in a solution due to dissociation (increasing i) or association (decreasing i).
72. The colligative property that results in the lowering of the vapor pressure of a solution is called:
A. Boiling point elevation
B. Freezing point depression
C. Vapor pressure lowering
D. Osmotic pressure
Answer: C. Vapor pressure lowering
Explanation:
Vapor pressure lowering is a colligative property caused by the addition of a non-volatile solute to a solvent, which reduces the vapor pressure of the solvent.
73. Which of the following solutions would have the lowest freezing point?
A. 0.1 M NaCl
B. 0.1 M glucose
C. 0.1 M K₂SO₄
D. 0.1 M urea
Answer: C. 0.1 M K₂SO₄
Explanation:
K₂SO₄ dissociates into three ions (2 K⁺ and 1 SO₄²⁻), creating the most solute particles in the solution, resulting in the greatest freezing point depression.
74. Raoult’s law is applicable to:
A. Ideal solutions only
B. Non-ideal solutions
C. Concentrated solutions only
D. Saturated solutions only
Answer: A. Ideal solutions only
Explanation:
Raoult’s law applies to ideal solutions where the interactions between the solute and solvent are similar to those between solvent-solvent and solute-solute interactions.
75. If a non-volatile solute is added to a volatile solvent, which of the following changes occurs?
A. The vapor pressure of the solvent increases
B. The boiling point of the solution decreases
C. The freezing point of the solution decreases
D. The vapor pressure of the solvent remains constant
Answer: C. The freezing point of the solution decreases
Explanation:
The addition of a non-volatile solute lowers the freezing point of the solvent, as fewer solvent molecules are able to form a solid phase.
76. Which of the following solutions will have the highest vapor pressure?
A. 0.1 M glucose
B. 0.1 M NaCl
C. 0.1 M K₂SO₄
D. 0.1 M urea
Answer: A. 0.1 M glucose
Explanation:
Glucose is a non-electrolyte and does not dissociate into ions, resulting in fewer solute particles compared to NaCl or K₂SO₄. Therefore, 0.1 M glucose will have the highest vapor pressure.
77. The process of osmosis involves:
A. Movement of solute molecules from low concentration to high concentration
B. Movement of solvent molecules through a semi-permeable membrane
C. Movement of solute molecules through a semi-permeable membrane
D. No movement of molecules
Answer: B. Movement of solvent molecules through a semi-permeable membrane
Explanation:
Osmosis involves the movement of solvent molecules from a region of low solute concentration to high solute concentration through a semi-permeable membrane.
78. Which of the following is not a colligative property?
A. Vapor pressure lowering
B. Surface tension
C. Boiling point elevation
D. Freezing point depression
Answer: B. Surface tension
Explanation:
Surface tension is not a colligative property. Colligative properties depend on the number of solute particles, while surface tension depends on intermolecular forces at the surface.
79. In a solution that shows positive deviation from Raoult’s law:
A. The solute-solvent interactions are stronger than solvent-solvent interactions
B. The solute-solvent interactions are weaker than solvent-solvent interactions
C. The vapor pressure is lower than predicted by Raoult’s law
D. The boiling point of the solution is higher than that of the pure solvent
Answer: B. The solute-solvent interactions are weaker than solvent-solvent interactions
Explanation:
Positive deviation from Raoult’s law occurs when the solute-solvent interactions are weaker than solvent-solvent and solute-solute interactions, leading to higher vapor pressure.
80. Which of the following solutions will have the highest boiling point?
A. 0.1 M glucose
B. 0.1 M NaCl
C. 0.1 M CaCl₂
D. 0.1 M urea
Answer: C. 0.1 M CaCl₂
Explanation:
CaCl₂ dissociates into three ions (Ca²⁺ and 2 Cl⁻), resulting in the highest number of solute particles in solution, which leads to the greatest boiling point elevation.
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