Solutions — Class 12 Chemistry

1. Molality (m) is defined as:

1. Moles of solute per liter of solution
2. Moles of solute per kilogram of solvent ✅
3. Mass percent of solute
4. Moles of solute per mole of solution

2. Raoult's law applies exactly to:

1. All real solutions
2. Ideal solutions ✅
3. Electrolyte solutions only
4. Colloidal solutions

3. Colligative properties depend on:

1. Chemical nature of solute
2. Number of solute particles in solution ✅
3. Color of solution
4. Density only

4. Boiling point elevation ΔT_b is directly proportional to:

1. Solvent molar mass only
2. Molality of solute ✅
3. Vapour pressure of solute
4. Square of concentration

5. The van't Hoff factor i accounts for:

1. Non-ideality of solvent
2. Degree of dissociation of electrolyte into ions ✅
3. Temperature dependence only
4. Viscosity changes

6. Osmotic pressure Π for dilute solutions is given by:

1. Π = mRT
2. Π = MRT ✅ (M = molarity of solute)
3. Π = Kb · m
4. Π = ΔT_f / K_f

7. Freezing point depression ΔT_f is larger for which of the following solutions (same molalities):

1. Non-electrolyte solution
2. Electrolyte solution that dissociates into more particles ✅
3. Solution with higher solvent molar mass only
4. Pure solvent

8. Mole fraction of solvent (x_solvent) in an ideal solution is related to vapour pressure by:

1. p = p° / x
2. p = x p° ✅ (Raoult's law)
3. p = x + p°
4. p = p° - x

9. For a solution of non-volatile solute in a volatile solvent, the vapour consists mainly of:

1. Both solute and solvent equally
2. Solvent molecules ✅
3. Only solute particles
4. Neither

10. When a non-electrolyte solute is dissolved in a solvent, which property changes depend only on number of particles?

1. Color
2. Colligative properties ✅
3. Reactivity
4. Density only

11. Which concentration unit does not change with temperature?

1. Molarity
2. Molality ✅
3. Volume percent
4. Mole percent

12. A solution shows negative deviation from Raoult's law when:

1. Intermolecular forces between A and B are weaker than A-A and B-B
2. A–B interactions are stronger than A–A and B–B ✅
3. No interactions exist
4. Solution is ideal only

13. The elevation in boiling point is independent of:

1. Molal concentration of solute
2. Nature of solute (for ideal dilute solutions) ✅
3. Solvent's ebullioscopic constant K_b
4. van't Hoff factor i

14. Which of the following is used to determine molar mass of a non-volatile solute?

1. Osmotic pressure measurements ✅
2. Conductivity only
3. Colorimetry
4. pH measurement

15. For dilute solutions, which two concentration units are approximately equal for aqueous solutions at room temperature?

1. Molarity and molality are vastly different
2. Molarity and molality (approx.) ✅
3. Mass percent and mole fraction
4. Normality and molality

16. Which of the following solutions will show the greatest freezing point depression (same molalities)?

1. 1 molal glucose (non-electrolyte)
2. 1 molal NaCl (electrolyte, approx. i=2) ✅
3. 1 molal sucrose (non-electrolyte)
4. Pure solvent

17. In an ideal solution, the partial vapour pressure of component A is proportional to:

1. Concentration of B only
2. Mole fraction of A ✅
3. Mass percent of A
4. Volume fraction only

18. Which statement about osmotic pressure is FALSE?

1. It increases with solute concentration
2. It is a colligative property
3. It depends on identity of solute even at low concentration ✅
4. It can be used to measure molar mass

19. The molar mass of a polymer is best determined using:

1. Freezing point depression
2. Osmotic pressure ✅
3. Boiling point elevation
4. Vapour pressure lowering

20. If a solution shows positive deviation from Raoult's law, its total vapour pressure is:

1. Less than that predicted by Raoult's law
2. Greater than that predicted by Raoult's law ✅
3. Equal always
4. Zero

21. The lowering of vapour pressure of a solvent by a non-volatile solute is given by:

1. Δp = p°(1 + x_solute)
2. Δp = p° x_solute (approx.) ✅
3. Δp = p°/x_solute
4. Δp = 0 always

22. For calculating molar mass using freezing point depression, which constant is required?

1. Ebullioscopic constant K_b
2. Cryoscopic constant K_f ✅
3. Osmotic constant only
4. van't Hoff factor only

23. Normality (N) is defined as:

1. Moles of solute per liter
2. Number of equivalents of solute per liter of solution ✅
3. Mass percent per liter
4. Mole fraction per liter

24. The boiling point elevation constant K_b depends on:

1. Nature of solute only
2. Nature of solvent ✅
3. Concentration only
4. Pressure only

25. A solution of glucose (C6H12O6) in water is ideal and non-electrolyte. Which is true about its vapour pressure compared to pure water?

1. Higher than pure water
2. Lower than pure water ✅
3. Equal to pure water
4. Zero

26. Which of these concentration units is temperature dependent?

1. Molality
2. Molarity ✅
3. Mole fraction
4. Mass percent

27. The osmotic pressure of 0.1 M solution of a non-electrolyte at 300 K is approximately (R = 0.0821 L·atm·K⁻¹·mol⁻¹):

1. 2.46 atm
2. 2.46 atm ✅ (Π = MRT = 0.1×0.0821×300 ≈ 2.463)
3. 0.0821 atm
4. 24.63 atm

28. In calculating molar mass from ebullioscopy, which measured quantity is needed?

1. Vapour pressure lowering only
2. Boiling point elevation ΔT_b ✅
3. Osmotic pressure only
4. Mole fraction only

29. Which solution property is used by cells to prevent bursting due to osmotic pressure?

1. Viscosity
2. Tonicity (isotonic solutions prevent bursting) ✅
3. Color
4. Conductivity only

30. Which of the following causes a solution to deviate positively from Raoult's law?

1. Strong A–B attractions
2. Weak A–B interactions compared to A–A and B–B ✅
3. Formation of complex between A and B
4. Identical molecules only

31. The mole fraction of solute in an extremely dilute solution is approximately equal to:

1. 1
2. Mole fraction ≈ moles of solute / total moles ≈ very small value near 0 ✅
3. 100%
4. Molality

32. Which of these methods gives direct measurement of vapour pressure of a liquid?

1. Freezing point apparatus
2. Isoteniscope / vapor pressure osmometer ✅
3. pH meter
4. Conductivity meter

33. Which of the following is TRUE for ideal dilute solutions of electrolytes?

1. They show no colligative effects
2. They follow colligative property relations when effective particle number accounted by i ✅
3. They always behave non-ideally
4. They have zero osmotic pressure

34. Which concentration unit expresses amount of substance per 100 g of solution?

1. Molarity
2. Mass percent ✅
3. Molality
4. Normality

35. Which of the following would decrease the osmotic pressure of a solution at constant temperature?

1. Increasing solute concentration
2. Decreasing solute concentration ✅
3. Raising temperature
4. Adding a non-volatile solute

36. The cryoscopic constant K_f is a property of:

1. Solute only
2. Solvent ✅
3. Solution as a whole
4. Temperature only

37. A solution containing electrolyte shows lower vapour pressure than expected because:

1. Electrolyte increases volatility
2. Dissociation increases effective particle number, lowering vapour pressure more ✅
3. Electrolyte evaporates easily
4. Temperature decreases only

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

1. Osmotic pressure
2. Viscosity ✅
3. Freezing point depression
4. Boiling point elevation

39. The boiling point of a 0.5 m aqueous solution of a non-electrolyte (Kb for water = 0.512 °C·kg·mol⁻¹) is approximately (assume i=1):

1. 100.256 °C
2. 100.256 °C ✅ (ΔT_b = K_b·m = 0.512×0.5 = 0.256; add to 100)
3. 99.744 °C
4. 101 °C

40. Which of the following increases with the addition of a non-volatile solute to a solvent?

1. Vapour pressure of solution
2. Boiling point of solution ✅
3. Freezing point of solution
4. None of the above

41. For an ideal solution of two volatile components A and B, total vapour pressure is:

1. p_total = pA° + pB°
2. p_total = xA pA° + xB pB° ✅
3. p_total = xA + xB
4. p_total = pA° / pB°

42. Which concentration unit is most appropriate for expressing colligative effects?

1. Molarity
2. Molality (temperature independent) ✅
3. Volume percent
4. Mass percent

43. Which of these is a consequence of adding salt to roads in winter?

1. Increase freezing point of water
2. Decrease freezing point of water (freezing point depression) ✅
3. No effect on freezing point
4. Increase vapour pressure

44. The molarity of a 1 molal solution of a solute in water at 25 °C is approximately:

1. Exactly 1 M
2. Approximately 1 M (since density of water ~1 kg L⁻¹) ✅
3. 0.1 M
4. 10 M

45. Which of the following will lower the vapour pressure of a solvent most at given molar concentration?

1. Volatile solute with high vapour pressure
2. Non-volatile solute (no vapour contribution) ✅
3. Pure solvent
4. Adding more solvent

46. For an ionic solute that completely dissociates into 3 ions, the ideal van't Hoff factor i is approximately:

1. 1
2. 3 ✅
3. 2
4. 0

47. Which experimental method measures osmotic pressure directly?

1. Ebullioscopy
2. Osmometer ✅
3. Cryoscopy
4. pH meter

48. Which of the following is used to describe non-ideal solution behavior quantitatively?

1. van't Hoff factor only
2. Activity and activity coefficients ✅
3. Only molarity
4. Standard state removal only

49. The freezing point of sea water is lower than pure water because of:

1. Higher pressure at sea level
2. Dissolved salts (colligative freezing point depression) ✅
3. Presence of plankton only
4. Higher boiling point