NEET UG - Vapour pressure of solutions, Raoult's law, ideal and non-ideal solutions, colligative properties and determination of molecular mass, van't Hoff factor Online Test (MCQ Quiz)

1. What is the definition of vapour pressure of a liquid?

A) The pressure exerted by the liquid molecules in the solid state. B) The pressure exerted by the liquid molecules in the gaseous state in equilibrium with the liquid at a given temperature. C) The pressure required to boil a liquid. D) The pressure exerted by the atmosphere on the surface of the liquid.

2. How does the vapour pressure of a pure solvent change with increasing temperature?

A) Decreases B) Increases C) Remains constant D) First increases, then decreases

3. According to Raoult's law, the partial vapour pressure of a volatile component in a solution is directly proportional to its:

A) Mole fraction in the liquid phase B) Mole fraction in the vapour phase C) Molality D) Molarity

4. For a binary solution of two volatile components A and B, Raoult's law can be expressed as:

A) P_total = P_A° * x_A + P_B° * x_B B) P_A = P_A° * x_A C) P_B = P_B° * x_B D) P_total = P_A° + P_B°

5. What is the total vapour pressure of an ideal solution according to Raoult's law?

A) Sum of partial pressures of individual components B) Sum of vapour pressures of pure components C) Product of mole fractions and vapour pressures of pure components D) Average of vapour pressures of pure components

6. An ideal solution is one that:

A) Obeys Raoult's law only at infinite dilution. B) Obeys Raoult's law under all conditions of temperature and concentration. C) Shows deviation from Raoult's law. D) Has components with significantly different intermolecular forces.

7. Which of the following is a characteristic of an ideal solution?

A) ΔH_mix = 0, ΔV_mix = 0 B) ΔH_mix > 0, ΔV_mix > 0 C) ΔH_mix < 0, ΔV_mix < 0 D) ΔH_mix ≠ 0, ΔV_mix ≠ 0

8. A non-ideal solution is one that:

A) Obeys Raoult's law under all conditions. B) Does not obey Raoult's law. C) Has zero enthalpy of mixing. D) Has zero volume of mixing.

9. Non-ideal solutions that show positive deviation from Raoult's law exhibit:

A) P_total < P_A° * x_A + P_B° * x_B B) P_total > P_A° * x_A + P_B° * x_B C) P_A < P_A° * x_A D) P_B < P_B° * x_B

10. For a non-ideal solution showing positive deviation, the intermolecular forces between solvent-solvent and solute-solute are generally: than solvent-solute interactions.

A) Weaker B) Stronger C) Equal D) Negligible

11. Which of the following pairs forms a non-ideal solution with positive deviation?

A) Benzene and Toluene B) Acetone and Ethanol C) Chloroform and Acetone D) Water and Hydrochloric acid

12. Non-ideal solutions that show negative deviation from Raoult's law exhibit:

A) P_total > P_A° * x_A + P_B° * x_B B) P_total < P_A° * x_A + P_B° * x_B C) P_A > P_A° * x_A D) P_B > P_B° * x_B

13. For a non-ideal solution showing negative deviation, the enthalpy of mixing (ΔH_mix) is typically:

A) Positive B) Negative C) Zero D) Indeterminate

14. Which of the following pairs forms a non-ideal solution with negative deviation?

A) Acetone and Carbon disulphide B) Ethanol and Water C) Benzene and Hexane D) n-Hexane and n-Heptane

15. Azeotropes are solutions that:

A) Boil at a constant temperature and have the same composition in the liquid and vapour phases. B) Show no deviation from Raoult's law. C) Have components with very weak intermolecular forces. D) Can be separated into pure components by fractional distillation.

16. Minimum boiling azeotropes are formed by solutions showing:

A) Negative deviation from Raoult's law B) Positive deviation from Raoult's law C) No deviation from Raoult's law D) Ideal behaviour

17. Maximum boiling azeotropes are formed by solutions showing:

A) Positive deviation from Raoult's law B) Negative deviation from Raoult's law C) Ideal behaviour D) Zero deviation from Raoult's law

18. Colligative properties depend on:

A) The nature of the solute particles. B) The total number of solute particles, irrespective of their nature. C) The amount of solvent. D) The molecular weight of the solute.

19. Which of the following is NOT a colligative property?

A) Relative lowering of vapour pressure B) Elevation of boiling point C) Depression of freezing point D) Osmotic pressure

20. The relative lowering of vapour pressure of a solvent is equal to the mole fraction of the:

A) Solvent B) Solute C) Solution D) Vapour

21. For a dilute solution, the relative lowering of vapour pressure is given by:

A) P° - P_s / P° = n / N B) P° - P_s / P_s = n / N C) P° - P_s / P° = N / n D) P° - P_s / P° = n / (n+N)

22. Elevation of boiling point (ΔT_b) is directly proportional to the molality (m) of the solution. The proportionality constant is known as:

A) Ebullioscopic constant (K_b) B) Cryoscopic constant (K_f) C) Gas constant (R) D) Boiling point constant

23. The unit of ebullioscopic constant (K_b) is:

A) K kg mol⁻¹ B) K mol kg⁻¹ C) mol kg⁻¹ K⁻¹ D) K kg mol

24. Depression of freezing point (ΔT_f) is directly proportional to the molality (m) of the solution. The proportionality constant is known as:

A) Ebullioscopic constant (K_b) B) Cryoscopic constant (K_f) C) Gas constant (R) D) Freezing point constant

25. The unit of cryoscopic constant (K_f) is:

A) K kg mol⁻¹ B) K mol kg⁻¹ C) mol kg⁻¹ K⁻¹ D) K kg mol

26. Osmotic pressure (Π) of a solution is given by the formula:

A) Π = nRT / V B) Π = nRT * V C) Π = V / nRT D) Π = n / (RT * V)

27. What is the relationship between osmotic pressure (Π), molar concentration (C), gas constant (R), and absolute temperature (T)?

A) Π = CRT B) Π = C / RT C) Π = RT / C D) Π = C + RT

28. Isotonic solutions are solutions that have:

A) The same boiling point. B) The same freezing point. C) The same osmotic pressure. D) The same vapour pressure.

29. Reverse osmosis is a process where:

A) Solvent moves from a region of higher solute concentration to a region of lower solute concentration. B) Solvent moves from a region of lower solute concentration to a region of higher solute concentration. C) Solute moves from a region of higher concentration to a region of lower concentration. D) Solvent moves across a semipermeable membrane due to pressure difference.

30. The van't Hoff factor (i) is used to account for the:

A) Deviation from Raoult's law. B) Association or dissociation of solute particles in solution. C) Intermolecular forces between solvent molecules. D) Boiling point elevation.

31. For a non-electrolyte solute that does not dissociate or associate in solution, the van't Hoff factor (i) is:

A) Greater than 1 B) Less than 1 C) Equal to 1 D) Zero

32. If a solute dissociates into 'n' ions in solution, and the degree of dissociation is α, the van't Hoff factor 'i' is given by:

A) 1 + α(n-1) B) 1 - α(n-1) C) 1 + α/n D) 1 - α/n

33. If a solute associates to form 'n' particles in solution, and the degree of association is α, the van't Hoff factor 'i' is given by:

A) 1 + α(1/n - 1) B) 1 - α(1/n - 1) C) 1 + α(n-1) D) 1 - α(n-1)

34. For NaCl, which dissociates into Na⁺ and Cl⁻ ions, the theoretical van't Hoff factor is:

A) 1 B) 2 C) 3 D) 4

35. For a solution of acetic acid in water, which undergoes partial dissociation, the van't Hoff factor (i) is typically:

A) Equal to 1 B) Greater than 1 but less than 2 C) Equal to 2 D) Less than 1

36. The van't Hoff factor can be used to modify the colligative property expressions. For example, elevation of boiling point becomes:

A) ΔT_b = i * K_b * m B) ΔT_b = K_b * m / i C) ΔT_b = K_b * m D) ΔT_b = i * K_b / m

37. The determination of molecular mass of a solute using colligative properties relies on the fact that colligative properties are:

A) Dependent on the nature of the solute. B) Dependent on the number of solute particles. C) Independent of temperature. D) Independent of the solvent.

38. To determine the molecular mass of a non-volatile solute using the elevation of boiling point method, the formula is:

A) M = (K_b * w) / (ΔT_b * W) B) M = (K_b * W) / (ΔT_b * w) C) M = (ΔT_b * w) / (K_b * W) D) M = (w * W) / (K_b * ΔT_b)

39. In the formula for determining molecular mass from freezing point depression (M = (K_f * w) / (ΔT_f * W)), 'w' represents:

A) Mass of the solvent in kg B) Mass of the solute in grams C) Mass of the solvent in grams D) Mass of the solute in kg

40. Osmotic pressure is particularly useful for determining the molecular mass of:

A) Ionic compounds B) Polymers and macromolecules C) Volatile solutes D) Gases

41. Which colligative property is generally preferred for determining the molecular mass of macromolecules?

A) Relative lowering of vapour pressure B) Elevation of boiling point C) Depression of freezing point D) Osmotic pressure

42. When a non-volatile solute is dissolved in a solvent, the vapour pressure of the solvent:

A) Increases B) Decreases C) Remains unchanged D) Becomes zero

43. The vapour pressure of a solution is always lower than that of the pure solvent at the same temperature due to:

A) Increased intermolecular forces. B) Decreased surface area. C) Presence of non-volatile solute particles on the surface. D) Increased rate of evaporation.

44. A solution that boils at a temperature higher than the boiling point of the pure solvent is said to exhibit:

A) Freezing point depression B) Boiling point elevation C) Osmotic pressure D) Vapour pressure lowering

45. If the degree of dissociation of an electrolyte is 1 (complete dissociation), the van't Hoff factor 'i' is equal to:

A) The number of ions produced per molecule B) The number of moles of solute C) The number of moles of solvent D) 1

46. Which of the following statements about Raoult's law is INCORRECT?

A) It applies to ideal solutions. B) It states that the partial pressure of a component is proportional to its mole fraction. C) It is applicable to solutions of non-volatile solutes. D) It describes the behaviour of real solutions under all conditions.

47. The depression in freezing point of a solvent upon addition of a solute is a colligative property because it depends on:

A) The chemical nature of the solvent. B) The physical state of the solute. C) The concentration of the solute particles. D) The rate of cooling.

48. A solution of glucose in water and a solution of sucrose in water, both having the same molar concentration, will have the same:

A) Boiling point B) Freezing point C) Osmotic pressure D) Vapour pressure

Vapour pressure of solutions, Raoult's law, ideal and non-ideal solutions, colligative properties and determination of molecular mass, van't Hoff factor - Online Test

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