90. Osmotic pressure depends on:
A. The volume of solvent
B. The type of solute
C. The number of solute particles in the solution
D. The molecular weight of solute
Answer: C. The number of solute particles in the solution
Explanation:
Osmotic pressure is a colligative property that depends on the concentration of solute particles in the solution, not their type or molecular weight.
91. Which of the following substances will not cause a depression in freezing point when dissolved in water?
A. NaCl
B. Glucose
C. Benzene
D. Urea
Answer: C. Benzene
Explanation:
Benzene is non-polar and immiscible in water, so it will not dissolve and therefore will not affect the freezing point of water.
92. The correct van’t Hoff factor for the electrolyte Al₂(SO₄)₃ in aqueous solution is:
A. 3
B. 4
C. 5
D. 6
Answer: C. 5
Explanation:
Al₂(SO₄)₃ dissociates into 2 Al³⁺ ions and 3 SO₄²⁻ ions, giving a total of 5 ions. Therefore, the van’t Hoff factor (i) is 5.
93. Which of the following will show the highest freezing point depression?
A. 0.1 M glucose
B. 0.1 M NaCl
C. 0.1 M BaCl₂
D. 0.1 M AlCl₃
Answer: D. 0.1 M AlCl₃
Explanation:
AlCl₃ dissociates into four ions (Al³⁺ and 3 Cl⁻), which results in the greatest number of solute particles, leading to the largest freezing point depression.
94. An ideal solution is formed when:
A. The solute-solute interactions are stronger than solvent-solvent interactions
B. The solute-solvent interactions are stronger than solvent-solvent interactions
C. The solute-solvent interactions are similar to solute-solute and solvent-solvent interactions
D. The vapor pressure of the solution is higher than that of the solvent
Answer: C. The solute-solvent interactions are similar to solute-solute and solvent-solvent interactions
Explanation:
An ideal solution forms when the interactions between solute and solvent molecules are similar to those between solvent molecules and between solute molecules. This results in no deviation from Raoult’s law.
95. Which of the following is not a colligative property?
A. Boiling point elevation
B. Vapor pressure lowering
C. Freezing point depression
D. Surface tension
Answer: D. Surface tension
Explanation:
Surface tension is not a colligative property. Colligative properties depend on the number of solute particles in solution, while surface tension is related to the intermolecular forces at the surface of a liquid.
96. In an ideal solution, the enthalpy of mixing is:
A. Positive
B. Negative
C. Zero
D. Unpredictable
Answer: C. Zero
Explanation:
In an ideal solution, the enthalpy of mixing is zero because there is no heat change upon mixing the solute and solvent, as their interactions are similar to those in the pure components.
97. Raoult’s law is applicable to which of the following?
A. Non-ideal solutions
B. Dilute solutions
C. Ideal solutions
D. Concentrated solutions
Answer: C. Ideal solutions
Explanation:
Raoult’s law applies to ideal solutions where the partial vapor pressure of each component is directly proportional to its mole fraction in the solution.
98. The colligative property that can be used to measure the molar mass of a protein is:
A. Vapor pressure lowering
B. Boiling point elevation
C. Freezing point depression
D. Osmotic pressure
Answer: D. Osmotic pressure
Explanation:
Osmotic pressure is commonly used to determine the molar mass of large molecules like proteins because it is sensitive to the number of solute particles in the solution.
99. For a solution of a non-electrolyte, the van’t Hoff factor (i) is:
A. 0
B. 1
C. 2
D. 3
Answer: B. 1
Explanation:
For a non-electrolyte, the van’t Hoff factor is 1 because the solute does not dissociate into ions, meaning the number of solute particles in the solution is the same as the number of solute molecules.
100. The addition of a non-volatile solute to a solvent will:
A. Increase the vapor pressure of the solvent
B. Decrease the vapor pressure of the solvent
C. Increase the freezing point of the solvent
D. Decrease the boiling point of the solvent
Answer: B. Decrease the vapor pressure of the solvent
Explanation:
The addition of a non-volatile solute reduces the number of solvent molecules at the surface, lowering the vapor pressure of the solvent
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