81. The depression in freezing point for a solution is greater if:
A. The number of solute particles is greater
B. The number of solute particles is smaller
C. The solution is more dilute
D. The solution is saturated
Answer: A. The number of solute particles is greater
Explanation:
Freezing point depression is directly proportional to the number of solute particles in the solution. More solute particles result in a greater depression in freezing point.
82. Which of the following statements is true for an ideal solution?
A. The total volume changes after mixing
B. The total vapor pressure is not proportional to the mole fractions of the components
C. The solution obeys Raoult’s law
D. There is a heat exchange during mixing
Answer: C. The solution obeys Raoult’s law
Explanation:
An ideal solution obeys Raoult’s law, where the partial vapor pressure of each component is directly proportional to its mole fraction in the solution.
83. Colligative properties are useful in determining:
A. The chemical structure of a solute
B. The molecular weight of a solute
C. The density of a solution
D. The boiling point of a solvent
Answer: B. The molecular weight of a solute
Explanation:
Colligative properties, such as freezing point depression and osmotic pressure, are used to determine the molecular weight of a solute by analyzing the effect of solute particles on the solution’s properties.
84. Which of the following will have the lowest freezing point?
A. 0.1 M glucose
B. 0.1 M NaCl
C. 0.1 M BaCl₂
D. 0.1 M urea
Answer: C. 0.1 M BaCl₂
Explanation:
BaCl₂ dissociates into three ions (Ba²⁺ and 2 Cl⁻), giving more solute particles than NaCl or glucose, which leads to the greatest freezing point depression, resulting in the lowest freezing point.
85. In a solution showing a negative deviation from Raoult’s law:
A. The vapor pressure is higher than expected
B. The vapor pressure is lower than expected
C. The boiling point is lower than expected
D. The freezing point is higher than expected
Answer: B. The vapor pressure is lower than expected
Explanation:
Negative deviation from Raoult’s law occurs when the solute-solvent interactions are stronger than the solvent-solvent interactions, resulting in a lower vapor pressure than predicted.
86. Colligative properties are dependent upon:
A. The type of solute particles
B. The number of solute particles
C. The chemical nature of the solvent
D. The temperature of the solvent
Answer: B. The number of solute particles
Explanation:
Colligative properties depend on the number of solute particles in the solution, regardless of their type or chemical nature.
87. A solution of KCl in water will exhibit:
A. Positive deviation from Raoult’s law
B. Negative deviation from Raoult’s law
C. Ideal behavior
D. Non-volatile solute behavior
Answer: C. Ideal behavior
Explanation:
KCl is an electrolyte, and its solutions typically behave ideally because the dissociation of ions results in proportional vapor pressure lowering, consistent with Raoult’s law.
88. The boiling point of a solution is higher than that of the pure solvent because:
A. The vapor pressure of the solution is higher than that of the solvent
B. The vapor pressure of the solution is lower than that of the solvent
C. The freezing point of the solution is higher than that of the solvent
D. The solute increases the surface tension of the solution
Answer: B. The vapor pressure of the solution is lower than that of the solvent
Explanation:
The addition of a non-volatile solute lowers the vapor pressure of the solvent, which means the solution must be heated to a higher temperature to reach the boiling point, where its vapor pressure equals the atmospheric pressure.
89. A solution shows positive deviation from Raoult’s law if:
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 of the solution is lower than expected
D. The solution freezes at a higher temperature than the solvent
Answer: B. The solute-solvent interactions are weaker than solvent-solvent interactions
Explanation:
Positive deviation occurs when the interactions between solute and solvent molecules are weaker than those between solvent molecules, causing the vapor pressure to be higher than expected.
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