Class 12 Chemistry – Chapter 2: Solutions

 

Class 12 Chemistry – Chapter 2: Solutions

Competitive / JEE Level – Questions Only

1. Define molarity, molality, mole fraction and mass percentage. Derive the relationship between molarity and molality.
2. Calculate the molality of a solution containing 18 g of glucose dissolved in 180 g of water.
3. A solution contains 5.85 g of NaCl in 500 g of water. Calculate its molality.
4. Calculate the mole fraction of ethanol and water in a solution containing 46 g ethanol and 54 g water.
5. A solution is prepared by dissolving 10 g of urea in 90 g of water. Calculate the mole fraction of urea.
6. 20 g of a non-volatile solute is dissolved in 180 g of water. The vapour pressure of the solution is 23.5 mm Hg while that of pure water is 24 mm Hg. Calculate the molar mass of the solute.
7. Derive Raoult's law for a solution containing volatile components.
8. Explain the difference between ideal and non-ideal solutions with suitable examples.
9. A solution containing two volatile liquids A and B obeys Raoult's law. Derive the expression for its total vapour pressure.
10. 10 g of a non-volatile solute is dissolved in 90 g of water. Calculate the relative lowering of vapour pressure if the molar mass of the solute is 100 g mol⁻¹.
11. Explain positive and negative deviations from Raoult's law.
12. What is an azeotrope? Explain the formation of minimum-boiling and maximum-boiling azeotropes.
13. Calculate the elevation in boiling point when 18 g glucose is dissolved in 500 g water.
    (Kb​=0.52 Kkgmol−1)
14. A solution containing 5 g of a non-electrolyte solute in 100 g water boils at 100.52∘C. Calculate the molar mass of the solute.
    (Kb​=0.52 Kkgmol−1)
15. Calculate the depression in freezing point when 9 g glucose is dissolved in 100 g water.
    (Kf​=1.86 Kkgmol−1)
16. A solution freezes at −0.372∘C. Calculate the molality of the solution.
    (Kf​=1.86 Kkgmol−1)
17. Explain the phenomenon of osmosis and define osmotic pressure.
18. Derive the equation for osmotic pressure of a dilute solution.
19. A solution contains 2 g of a polymer dissolved in 100 mL solution. Its osmotic pressure at 27°C is 0.246 atm. Calculate the molar mass of the polymer.
20. Calculate the osmotic pressure of a 0.1 M glucose solution at 27°C.
    (R=0.0821 LatmK−1mol−1)
21. Why is osmotic pressure preferred over other colligative properties for determining the molar mass of proteins and polymers?
22. Explain reverse osmosis and mention its practical application.
23. What are colligative properties? Explain why they depend only on the number of solute particles.
24. Derive the expression for depression in freezing point.
25. Derive the expression for elevation in boiling point.
26. A solution containing 1.8 g of glucose in 100 g water shows a depression in freezing point of 0.186∘C. Calculate the molar mass of glucose.
27. 1 g of a non-electrolyte solute dissolved in 100 g benzene produces a depression in freezing point of 0.5 K. Calculate the molar mass of the solute.
    (Kf​ for benzene=5.12 Kkgmol−1)
28. Explain abnormal molar mass with suitable examples.
29. Define the van't Hoff factor and derive its relation with observed and calculated colligative properties.
30. A 0.1 molal solution of CaCl2​ shows 80% ionisation. Calculate its effective molality.
31. Calculate the van't Hoff factor for Na2​SO4​ if its degree of dissociation is 60%.
32. A solution of K2​SO4​ is 50% dissociated. Calculate its van't Hoff factor.
33. A solute undergoes association to form dimers. Derive the expression for van't Hoff factor in terms of degree of association.
34. A 0.1 molal solution of an electrolyte has a freezing point depression of 0.279 K. Calculate its van't Hoff factor.
    (Kf​=1.86 Kkgmol−1)
35. A compound AB2​ dissociates into three ions with 70% dissociation. Calculate its van't Hoff factor.
36. A solute associates to form trimers. If the degree of association is 60%, calculate the van't Hoff factor.
37. Derive the relation between molar mass and elevation in boiling point.
38. Derive the relation between molar mass and depression in freezing point.
39. Explain why the addition of a non-volatile solute lowers the vapour pressure of a solvent.
40. JEE Level: A solution contains equal masses of glucose and sucrose dissolved in equal masses of water. Compare their osmotic pressures at the same temperature.
41. JEE Level: Two solutions have the same osmotic pressure at the same temperature. What relationship exists between their molar concentrations?
42. JEE Level: 0.1 M NaCl and 0.1 M glucose solutions are compared at the same temperature. Which has greater osmotic pressure? Explain using van't Hoff factor.
43. JEE Level: A solution contains NaCl with 90% ionisation. Calculate the van't Hoff factor and compare its freezing point depression with that of an ideal 0.1 m glucose solution.
44. JEE Level: A 1 g sample of a polymer is dissolved in enough water to make 100 mL solution. At 27°C, its osmotic pressure is 0.0821 atm. Calculate its molar mass.
45. JEE Level: A solution containing a non-volatile solute has a vapour pressure of 22.4 mm Hg at 25°C, while pure solvent has vapour pressure 24 mm Hg. Calculate the mole fraction of the solute.