Here below some basic MCQ’s about “Raoult’s law and colligative properties” with answer which is well explained. Let’s check one by one.
1. Raoult’s law is applicable to which type of solutions?
A. Ideal solutions
B. Non-ideal solutions
C. Dilute solutions only
D. Colloidal solutions
Answer: A. Ideal solutions
Explanation:
Raoult’s Law states that the vapor pressure of a volatile component in a solution is directly proportional to its mole fraction. This law is strictly applicable to ideal solutions, where the interactions between solute-solute, solvent-solvent, and solute-solvent molecules are similar.
2. Colligative properties depend on:
A. Nature of solute
B. Type of solvent
C. Number of solute particles
D. Pressure of the system
Answer: C. Number of solute particles
Explanation:
Colligative properties (like boiling point elevation, freezing point depression, vapor pressure lowering, and osmotic pressure) depend only on the number of solute particles in a solution, not on their nature or type. These properties arise because the addition of solute particles disrupts the physical properties of the solvent.
3. Which of the following is NOT a colligative property?
A. Vapor pressure lowering
B. Boiling point elevation
C. Osmotic pressure
D. Surface tension
Answer: D. Surface tension
Explanation:
Colligative properties include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure. Surface tension is a physical property that depends on the nature of the solvent and is not a colligative property.
4. According to Raoult’s Law, the relative lowering of vapor pressure is equal to:
A. The mole fraction of the solute
B. The mole fraction of the solvent
C. The number of solute particles
D. The total pressure of the system
Answer: A. The mole fraction of the solute
Explanation:
Raoult’s Law states that the relative lowering of vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solute. The equation is:
Relative lowering of vapor pressure=ΔPP0=xsoluteRelative lowering of vapor pressure=P0ΔP=xsolute
Where xsolutexsolute is the mole fraction of the solute.
5. Which colligative property can be used to determine molar mass of a solute?
A. Vapor pressure lowering
B. Surface tension
C. Boiling point elevation
D. Refractive index
Answer: C. Boiling point elevation
Explanation:
Boiling point elevation can be used to determine the molar mass of a solute. When a non-volatile solute is added to a solvent, the boiling point of the solution increases. This elevation is related to the molal concentration of the solute, which can be used to calculate its molar mass.
6. What happens to the freezing point of a solution when a solute is added to a solvent?
A. It increases
B. It decreases
C. It remains unchanged
D. It depends on the type of solute
Answer: B. It decreases
Explanation:
When a non-volatile solute is added to a solvent, the freezing point of the solution decreases. This is known as freezing point depression, a colligative property. The presence of solute particles interferes with the crystallization process of the solvent, lowering its freezing point.
7. Which statement about osmotic pressure is true?
A. It decreases with an increase in solute concentration
B. It is not affected by temperature
C. It is a colligative property
D. It is always zero in ideal solutions
Answer: C. It is a colligative property
Explanation:
Osmotic pressure is a colligative property because it depends on the number of solute particles in a solution. It increases with an increase in solute concentration and is directly proportional to temperature.
8. In an ideal solution, the total vapor pressure is:
A. Lower than predicted by Raoult’s Law
B. Higher than predicted by Raoult’s Law
C. Equal to the sum of the partial vapor pressures
D. Independent of the composition
Answer: C. Equal to the sum of the partial vapor pressures
Explanation:
In an ideal solution, the total vapor pressure is equal to the sum of the partial vapor pressures of the components, as described by Raoult’s Law. Each component’s partial vapor pressure is proportional to its mole fraction in the solution.
9. Which of the following statements is true regarding an ideal solution?
A. The enthalpy of mixing is zero
B. There is a large volume change during mixing
C. Raoult’s law is not applicable
D. The solution forms only at low temperatures
Answer: A. The enthalpy of mixing is zero
Explanation:
For an ideal solution, the enthalpy of mixing is zero, meaning no heat is absorbed or evolved during the mixing process. Additionally, the volume of the solution is the sum of the volumes of the components, with no expansion or contraction.
10. The depression in freezing point is proportional to:
A. The molality of the solution
B. The molarity of the solution
C. The mole fraction of the solute
D. The volume of the solution
Answer: A. The molality of the solution
Explanation:
The depression in freezing point is directly proportional to the molality (moles of solute per kilogram of solvent) of the solution. This is expressed as:
ΔTf=Kf⋅m
Where KfKf is the cryoscopic constant and mm is the molality.
11. The van’t Hoff factor (i) for NaCl in water is:
A. 1
B. 2
C. 3
D. 0
Answer: B. 2
Explanation:
NaCl dissociates into Na⁺ and Cl⁻ ions in water. Since it dissociates into two particles, the van’t Hoff factor (i) for NaCl is 2.
12. Raoult’s law is followed by:
A. All solutions
B. Solutions showing positive deviation
C. Solutions showing negative deviation
D. Ideal solutions
Answer: D. Ideal solutions
Explanation:
Raoult’s law is strictly followed by ideal solutions where the interactions between all components are uniform. Non-ideal solutions exhibit deviations from Raoult’s law.
13. Which of the following compounds will show the highest boiling point elevation when dissolved in water?
A. Glucose
B. NaCl
C. K₂SO₄
D. Urea
Answer: C. K₂SO₄
Explanation:
K₂SO₄ dissociates into 3 ions (2 K⁺ and 1 SO₄²⁻), so it will produce the most solute particles in solution, leading to the highest elevation in boiling point, as boiling point elevation is proportional to the number of particles.
14. The lowering of vapor pressure is a colligative property because it:
A. Depends on the nature of the solute
B. Depends on the mass of the solute
C. Depends on the number of solute particles
D. Is independent of the solvent
Answer: C. Depends on the number of solute particles
Explanation:
Lowering of vapor pressure is a colligative property because it depends on the number of solute particles in the solution, not the nature of the solute.
15. 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 BaCl₂
D. 0.1 M urea
Answer: C. 0.1 M BaCl₂
Explanation:
BaCl₂ dissociates into three particles (Ba²⁺ and 2 Cl⁻), leading to a higher effect on freezing point depression. The more particles present, the greater the freezing point depression.
16. Which of the following statements is correct about an ideal solution?
A. It shows a positive deviation from Raoult’s law
B. It shows a negative deviation from Raoult’s law
C. The enthalpy change of mixing is zero
D. The enthalpy of mixing is positive
Answer: C. The enthalpy change of mixing is zero
Explanation:
In an ideal solution, the enthalpy change of mixing is zero, meaning no heat is absorbed or evolved when the solute and solvent mix.
17. The osmotic pressure of a solution is directly proportional to:
A. The volume of the solvent
B. The number of solute particles
C. The temperature
D. Both B and C
Answer: D. Both B and C
Explanation:
Osmotic pressure is directly proportional to the number of solute particles in the solution and the temperature of the system. The relationship is given by Van’t Hoff’s equation for osmotic pressure.
18. Raoult’s law predicts that the partial vapor pressure of each volatile component in a solution is proportional to:
A. Its molality
B. Its mole fraction
C. Its molecular mass
D. The temperature
Answer: B. Its mole fraction
Explanation:
According to Raoult’s law, the partial vapor pressure of each component in an ideal solution is directly proportional to its mole fraction in the solution.
19. Which property does not change with the number of particles in a solution?
A. Boiling point elevation
B. Freezing point depression
C. Osmotic pressure
D. Density
Answer: D. Density
Explanation:
Density is not a colligative property, so it does not depend solely on the number of particles in the solution. Colligative properties like boiling point elevation, freezing point depression, and osmotic pressure are dependent on the number of solute particles.
20. The elevation in boiling point of a solution is directly proportional to the:
A. Molarity of the solution
B. Molality of the solution
C. Number of moles of solute
D. Mole fraction of solvent
Answer: B. Molality of the solution
Explanation:
The elevation in boiling point is directly proportional to the molality of the solution. The relation is given by:
ΔTb=Kb⋅m
Where mm is the molality and Kb is the ebullioscopic constant.
21. The colligative property that is most useful for determining the molar mass of polymers is:
A. Osmotic pressure
B. Boiling point elevation
C. Freezing point depression
D. Vapor pressure lowering
Answer: A. Osmotic pressure
Explanation:
Osmotic pressure is particularly useful in determining the molar mass of polymers because it is more sensitive for solutions with large molar masses, like polymers, where small changes in concentration affect the osmotic pressure significantly.
22. The relative lowering of vapor pressure of a solvent is equal to:
A. Mole fraction of solute
B. Mole fraction of solvent
C. Molality of solution
D. Molarity of solution
Answer: A. Mole fraction of solute
Explanation:
Raoult’s law states that the relative lowering of vapor pressure is directly proportional to the mole fraction of the solute in the solution.
23. A solution that shows positive deviation from Raoult’s law will have:
A. Strong solute-solvent interactions
B. Weak solute-solvent interactions
C. No interactions between solute and solvent
D. Equal solute-solvent and solvent-solvent interactions
Answer: B. Weak solute-solvent interactions
Explanation:
A solution that shows positive deviation from Raoult’s law has weaker solute-solvent interactions than solvent-solvent or solute-solute interactions, resulting in a higher vapor pressure than expected.
24. Colligative properties are applicable to which type of solutes?
A. Non-electrolytes only
B. Electrolytes only
C. Both electrolytes and non-electrolytes
D. Colloidal solutions
Answer: C. Both electrolytes and non-electrolytes
Explanation:
Colligative properties apply to both electrolytes and non-electrolytes, as they depend on the number of solute particles, whether they are molecules (non-electrolytes) or ions (electrolytes).
25. In an aqueous solution, the freezing point is lowered by 1.86°C when 1 mol of solute is dissolved in 1 kg of water. This constant is called:
A. Freezing point depression constant
B. Boiling point elevation constant
C. Osmotic constant
D. Van’t Hoff factor
Answer: A. Freezing point depression constant
Explanation:
The constant that represents the freezing point depression per molal concentration of a solute in a solvent is called the freezing point depression constant (K_f). For water, it is approximately 1.86°C·kg/mol.
26. Raoult’s law is applicable only to:
A. Electrolytic solutions
B. Nonelectrolytic solutions
C. Both electrolytic and nonelectrolytic solutions
D. Ideal solutions
Answer: D. Ideal solutions
Explanation:
Raoult’s law is strictly applicable to ideal solutions, where solute-solvent, solvent-solvent, and solute-solute interactions are similar. Non-ideal solutions show deviations from Raoult’s law.
27. Which of the following is not affected by the presence of a solute in a solution?
A. Freezing point
B. Boiling point
C. Vapour pressure
D. Density
Answer: D. Density
Explanation:
Colligative properties such as freezing point, boiling point, and vapor pressure are affected by the presence of a solute, whereas density is not directly a colligative property.
28. When a non-volatile solute is added to a volatile solvent, the vapor pressure of the solution:
A. Increases
B. Decreases
C. Remains the same
D. First increases, then decreases
Answer: B. Decreases
Explanation:
The addition of a non-volatile solute to a volatile solvent lowers the vapor pressure of the solvent. This happens because the solute particles occupy some of the surface area, reducing the number of solvent molecules that can escape into the vapor phase.
29. Which of the following is a colligative property?
A. Refractive index
B. Surface tension
C. Osmotic pressure
D. Viscosity
Answer: C. Osmotic pressure
Explanation:
Osmotic pressure is a colligative property, which depends only on the number of solute particles in a solution and not on their nature.
30. The colligative property used in desalination of water by reverse osmosis is:
A. Freezing point depression
B. Boiling point elevation
C. Vapor pressure lowering
D. Osmotic pressure
Answer: D. Osmotic pressure
Explanation:
Osmotic pressure is utilized in the process of reverse osmosis to desalinate water. By applying pressure greater than the osmotic pressure, pure water is forced through a semi-permeable membrane, leaving the solutes behind.
31. The freezing point of an aqueous solution is lower than that of pure water because:
A. The solute lowers the vapor pressure of the solvent
B. The solute raises the vapor pressure of the solvent
C. The solute raises the freezing point
D. The solute decreases the osmotic pressure
Answer: A. The solute lowers the vapor pressure of the solvent
Explanation:
The addition of a solute lowers the vapor pressure of the solvent, which results in a lower freezing point. This is known as freezing point depression.
32. A solution of NaCl in water freezes at a lower temperature than pure water because:
A. The vapor pressure of the solution is higher than that of pure water
B. NaCl is non-volatile
C. NaCl undergoes ionization in water
D. The boiling point of the solution is higher than that of pure water
Answer: C. NaCl undergoes ionization in water
Explanation:
NaCl dissociates into Na⁺ and Cl⁻ ions in water, increasing the number of solute particles, which causes a greater depression in the freezing point, leading to the solution freezing at a lower temperature than pure water.
33. Which of the following solutions will exhibit the highest osmotic pressure?
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⁻), producing more particles in solution. Since osmotic pressure is directly proportional to the number of solute particles, BaCl₂ will have the highest osmotic pressure.
34. Colligative properties of solutions are affected by:
A. Size of solute molecules
B. Shape of solute molecules
C. Number of solute particles
D. Color of the solute
Answer: C. Number of solute particles
Explanation:
Colligative properties depend only on the number of solute particles in the solution, regardless of their size, shape, or other physical characteristics.
35. In an ideal solution, the enthalpy of mixing is:
A. Positive
B. Negative
C. Zero
D. Infinite
Answer: C. Zero
Explanation:
For an ideal solution, the enthalpy of mixing is zero, meaning no heat is absorbed or released when the solute and solvent are mixed. The solution forms without any change in energy.
36. Which of the following factors does not affect the colligative properties of a solution?
A. Nature of solute
B. Number of solute particles
C. Molality of the solution
D. Van’t Hoff factor
Answer: A. Nature of solute
Explanation:
Colligative properties are not dependent on the nature of the solute but only on the number of solute particles, their concentration (molality), and the van’t Hoff factor.
37. The boiling point of a liquid increases when a solute is added because:
A. The solute increases the vapor pressure of the liquid
B. The solute decreases the vapor pressure of the liquid
C. The solute increases the density of the liquid
D. The solute decreases the density of the liquid
Answer: B. The solute decreases the vapor pressure of the liquid
Explanation:
When a solute is added, the vapor pressure of the solvent decreases. Consequently, a higher temperature is required to make the vapor pressure equal to the external pressure, thus increasing the boiling point.
38. The depression in freezing point is a colligative property because it:
A. Depends on the chemical nature of the solute
B. Depends on the number of solute particles
C. Depends on the freezing point of the solvent
D. Depends on the vapor pressure of the solute
Answer: B. Depends on the number of solute particles
Explanation:
Freezing point depression is a colligative property that depends solely on the number of solute particles present in the solution, not their chemical nature.
39. Which of the following statements is correct about vapor pressure lowering?
A. It increases with an increase in the mole fraction of the solute
B. It decreases with an increase in the mole fraction of the solute
C. It is independent of the number of solute particles
D. It depends on the molecular weight of the solute
Answer: A. It increases with an increase in the mole fraction of the solute
Explanation:
The relative lowering of vapor pressure increases with the mole fraction of the solute. More solute particles reduce the number of solvent molecules at the surface, decreasing the vapor pressure.
40. In a solution of a non-volatile solute in a volatile solvent, the vapor pressure of the solvent:
A. Increases
B. Decreases
C. Remains constant
D. Becomes zero
Answer: B. Decreases
Explanation:
In a solution, the vapor pressure of the solvent is lowered by the presence of a non-volatile solute. This occurs because the solute particles occupy some of the surface area, reducing the number of solvent molecules that can evaporate.
41. The osmotic pressure of a solution is related to the:
A. Volume of solvent
B. Concentration of solute particles
C. Nature of solute
D. Molecular weight of solute
Answer: B. Concentration of solute particles
Explanation:
Osmotic pressure is directly proportional to the concentration of solute particles in the solution. It is a colligative property, meaning it depends only on the number of solute particles.
42. Which of the following will have the lowest freezing point?
A. 0.1 M urea
B. 0.1 M glucose
C. 0.1 M NaCl
D. 0.1 M K₂SO₄
Answer: D. 0.1 M K₂SO₄
Explanation:
K₂SO₄ dissociates into three ions (2 K⁺ and 1 SO₄²⁻), creating the largest number of particles in the solution. Since freezing point depression is proportional to the number of particles, K₂SO₄ will cause the greatest freezing point depression.
43. When comparing solutions of the same concentration, which one will have the highest boiling point?
A. 1 M glucose
B. 1 M NaCl
C. 1 M CaCl₂
D. 1 M urea
Answer: C. 1 M CaCl₂
Explanation:
CaCl₂ dissociates into three ions (Ca²⁺ and 2 Cl⁻), producing the highest number of solute particles. This will result in the greatest elevation in boiling point, since boiling point elevation is proportional to the number of particles in solution.
44. In an ideal solution, the partial vapor pressure of a component is:
A. Higher than predicted by Raoult’s law
B. Lower than predicted by Raoult’s law
C. Equal to its mole fraction multiplied by the vapor pressure of the pure component
D. Independent of its mole fraction
Answer: C. Equal to its mole fraction multiplied by the vapor pressure of the pure component
Explanation:
According to Raoult’s law, in an ideal solution, the partial vapor pressure of a component is proportional to its mole fraction and the vapor pressure of the pure component.
45. The colligative property of vapor pressure lowering is used to:
A. Determine the boiling point of a solvent
B. Determine the molar mass of a solute
C. Determine the molecular structure of a solute
D. Determine the density of a solvent
Answer: B. Determine the molar mass of a solute
Explanation:
Vapor pressure lowering is a colligative property that can be used to determine the molar mass of a solute by measuring the change in vapor pressure when a solute is added to a solvent.
46. A solution that exhibits a negative deviation from Raoult’s law has:
A. Weaker solute-solvent interactions
B. Stronger solute-solvent interactions
C. No solute-solvent interactions
D. The same solute-solvent and solvent-solvent interactions
Answer: B. Stronger solute-solvent interactions
Explanation:
Negative deviation from Raoult’s law occurs when the solute-solvent interactions are stronger than the solute-solute and solvent-solvent interactions, leading to a lower vapor pressure than expected.
47. The molal depression constant (K_f) depends upon:
A. The nature of the solute
B. The nature of the solvent
C. The concentration of the solution
D. The temperature of the solution
Answer: B. The nature of the solvent
Explanation:
The molal depression constant (K_f) is a property of the solvent and depends only on the nature of the solvent. It represents the freezing point depression per molal concentration of a solute.
48. Colligative properties include all except:
A. Boiling point elevation
B. Freezing point depression
C. Surface tension
D. Osmotic pressure
Answer: C. Surface tension
Explanation:
Surface tension is not a colligative property. Colligative properties (boiling point elevation, freezing point depression, and osmotic pressure) depend on the number of solute particles in a solution.
49. 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 MgCl₂
D. 0.1 M urea
Answer: C. 0.1 M MgCl₂
Explanation:
MgCl₂ dissociates into three ions (Mg²⁺ and 2 Cl⁻), resulting in the largest number of solute particles in solution. The more particles there are, the greater the boiling point elevation.
50. The van’t Hoff factor (i) for a substance that does not dissociate in solution is:
A. 0
B. 1
C. 2
D. 3
Answer: B. 1
Explanation:
For substances that do not dissociate in solution, the van’t Hoff factor (i) is 1, as the number of particles in the solution is the same as the number of molecules of the solute.
51. The osmotic pressure of a solution is:
A. Directly proportional to the temperature
B. Directly proportional to the volume of solvent
C. Inversely proportional to the temperature
D. Independent of temperature
Answer: A. Directly proportional to the temperature
Explanation:
Osmotic pressure is directly proportional to the absolute temperature (T) and the number of solute particles in the solution, as given by the formula:
π=iCRTπ=iCRT
where ππ is osmotic pressure, ii is the van’t Hoff factor, CC is concentration, and TT is temperature.
52. When the solute-solvent interactions are weaker than the solute-solute and solvent-solvent interactions, the solution shows:
A. Positive deviation from Raoult’s law
B. Negative deviation from Raoult’s law
C. No deviation from Raoult’s law
D. Ideal behavior
Answer: A. Positive deviation from Raoult’s law
Explanation:
When solute-solvent interactions are weaker, the components escape more easily, resulting in a higher vapor pressure than predicted by Raoult’s law. This leads to positive deviation.
53. The colligative property that causes the freezing point of a solution to be lower than that of the pure solvent is called:
A. Freezing point elevation
B. Freezing point depression
C. Boiling point elevation
D. Vapor pressure lowering
Answer: B. Freezing point depression
Explanation:
Freezing point depression is the decrease in the freezing point of a solvent when a solute is dissolved in it. This is a colligative property dependent on the number of solute particles.
54. If a solution follows Raoult’s law, it is classified as:
A. An ideal solution
B. A non-ideal solution
C. A supersaturated solution
D. A saturated solution
Answer: A. An ideal solution
Explanation:
A solution that obeys Raoult’s law at all concentrations and temperatures is considered an ideal solution. In such solutions, solute-solvent interactions are similar to solvent-solvent and solute-solute interactions.
55. When 1 mole of NaCl is dissolved in water, it dissociates into:
A. 1 particle
B. 2 particles
C. 3 particles
D. 4 particles
Answer: B. 2 particles
Explanation:
NaCl dissociates into two ions in water: Na⁺ and Cl⁻. Thus, 1 mole of NaCl produces 2 particles in the solution.
56. The effect of adding a non-volatile solute to a volatile solvent is:
A. Elevation in boiling point
B. Depression in freezing point
C. Lowering of vapor pressure
D. All of the above
Answer: D. All of the above
Explanation:
The addition of a non-volatile solute to a volatile solvent lowers the vapor pressure, elevates the boiling point, and depresses the freezing point. These are colligative properties that depend on the number of solute particles.
57. Colligative properties are related to:
A. The physical properties of the solvent
B. The chemical properties of the solute
C. The number of particles in the solution
D. The nature of the solute particles
Answer: C. The number of particles in the solution
Explanation:
Colligative properties depend on the number of solute particles in the solution, regardless of their chemical or physical nature.
58. Raoult’s law applies to which of the following solutions?
A. Dilute solutions only
B. Concentrated solutions only
C. Ideal solutions only
D. Solutions of electrolytes only
Answer: C. Ideal solutions only
Explanation:
Raoult’s law is strictly followed by ideal solutions where the interactions between solute and solvent are similar to those between solvent molecules and between solute molecules.
59. The boiling point of an ideal solution is higher than that of the pure solvent because:
A. The solute increases the vapor pressure of the solution
B. The solute lowers the vapor pressure of the solution
C. The solute raises the freezing point of the solution
D. The solute decreases the osmotic pressure
Answer: B. The solute lowers the vapor pressure of the solution
Explanation:
When a solute is added to a solvent, the vapor pressure of the solution decreases. This leads to a higher boiling point since the solution must be heated more to reach the point where its vapor pressure equals atmospheric pressure.
60. In a solution of an electrolyte, the van’t Hoff factor (i) is greater than 1 because:
A. The solute molecules dissociate into ions
B. The solute molecules form complexes
C. The solvent dissociates into ions
D. The solute molecules undergo association
Answer: A. The solute molecules dissociate into ions
Explanation:
The van’t Hoff factor (i) is greater than 1 for electrolytes because they dissociate into ions, increasing the number of solute particles in the solution.
61. The vapor pressure of a solvent in a solution is proportional to:
A. The molality of the solution
B. The mole fraction of the solute
C. The mole fraction of the solvent
D. The concentration of the solution
Answer: C. The mole fraction of the solvent
Explanation:
According to Raoult’s law, the vapor pressure of the solvent in a solution is proportional to the mole fraction of the solvent in the solution.
62. The colligative property most useful in determining the molecular weight of macromolecules is:
A. Boiling point elevation
B. Freezing point depression
C. Osmotic pressure
D. Vapor pressure lowering
Answer: C. Osmotic pressure
Explanation:
Osmotic pressure is highly sensitive to changes in the concentration of solute particles, making it the most useful colligative property for determining the molecular weight of large macromolecules such as polymers.
63. Which of the following does not follow Raoult’s law?
A. Ideal solutions
B. Non-ideal solutions
C. Dilute solutions
D. Electrolyte solutions
Answer: B. Non-ideal solutions
Explanation:
Non-ideal solutions show deviations (positive or negative) from Raoult’s law due to differences in interactions between solute-solvent, solute-solute, and solvent-solvent molecules.
64. Which solution will show the greatest elevation in boiling point?
A. 0.1 M glucose
B. 0.1 M NaCl
C. 0.1 M AlCl₃
D. 0.1 M urea
Answer: C. 0.1 M AlCl₃
Explanation:
AlCl₃ dissociates into four ions (Al³⁺ and 3 Cl⁻), producing the most solute particles in the solution. Since boiling point elevation depends on the number of solute particles, AlCl₃ will show the greatest elevation.
65. The decrease in vapor pressure of a solvent in a solution is due to:
A. Increase in solvent molecules
B. The presence of solute particles
C. Increase in temperature
D. Increase in solvent volume
Answer: B. The presence of solute particles
Explanation:
The addition of solute particles reduces the number of solvent molecules at the surface, lowering the vapor pressure of the solvent.
66. Which of the following colligative properties is used to calculate the molar mass of a solute by measuring the decrease in the freezing point of a solvent?
A. Boiling point elevation
B. Freezing point depression
C. Vapor pressure lowering
D. Osmotic pressure
Answer: B. Freezing point depression
Explanation:
Freezing point depression is used to determine the molar mass of a solute. The extent of freezing point lowering depends on the number of solute particles in the solution.
67. The molal elevation constant (K_b) depends on:
A. The nature of the solute
B. The nature of the solvent
C. The concentration of the solution
D. The volume of the solvent
Answer: B. The nature of the solvent
Explanation:
The molal elevation constant (K_b) is a property of the solvent and represents the boiling point elevation per molal concentration of solute.
68. In a dilute solution, which of the following is true for colligative properties?
A. They depend on the nature of solute particles
B. They depend on the number of solute particles
C. They depend on the color of the solute
D. They depend on the molecular weight of the solute
Answer: B. They depend on the number of solute particles
Explanation:
Colligative properties depend only on the number of solute particles in the solution, irrespective of their chemical or physical properties.
69. The van’t Hoff factor for an electrolyte that dissociates completely in solution is:
A. Less than 1
B. Equal to 1
C. Greater than 1
D. Equal to zero
Answer: C. Greater than 1
Explanation:
For electrolytes that dissociate into ions, the van’t Hoff factor (i) is greater than 1 because the number of solute particles increases as the solute dissociates.
70. Which of the following is true for an ideal solution?
A. The enthalpy of mixing is positive
B. The enthalpy of mixing is negative
C. The enthalpy of mixing is zero
D. The volume of mixing increases
Answer: C. The enthalpy of mixing is zero
Explanation:
For an ideal solution, the enthalpy of mixing is zero, meaning there is no heat change when the solute and solvent are mixed.
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.
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.
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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