Solution chapter chemistry class 12 most important numericals

Chemistry class 12

Solution chapter most important numericals

1. Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL of water at 37°C.

2. When 19.5 g of F – CH2 – COOH (Molar mass = 78 g mol–1), is dissolved in 500 g of water, the depression in freezing point is observed to be 1°C. Calculate the degree of dissociation of F – CH2 – COOH.
[Given: Kf for water = 1.86 K kg mol–¹]

3. The freezing point of a solution containing 5 g of benzoic acid (M = 122gmol-¹) in 35 g of benzene is depressed by 2.94 K. What is the percentage association of benzoic acid if it forms a dimer in solution?
(Kf for benzene = 4.9Kkgmol-¹)

4.  3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).
(Given: Molar mass of benzoic acid = 122 g mol-1, Kf for benzene = 4.9 K kg mol-¹)

5. Calculate the mass of NaCl (molar mass = 58.5 g mol-¹) to be dissolved in 37.2 g of water to lower the freezing point by 2°C, assuming that NaCl undergoes complete dissociation. (Kf for water = 1.86 K kg mol-1)

6. Calculate the amount of NaCl (M = 58.5 g mol-1) that must be added to 100 g of water so that freezing point is depressed by 2 K. Kf for water is 1.86 K/m.

7.  2g of benzoic (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mol-1. What is the percentage association of acid if it forms dimer in solution?

8.  A solution contains 5.85 g NaCl (Molar mass = 58.5 g mol-¹) per litre of solution. It has an osmotic pressure of 4.75 atm at 27°C. Calculate the degree of dissociation of NaCl in this solution. (Given: R = 0.082 L atm K-¹ mol-¹)

9. A solution 0.1 M of Na2SO4 is dissolved to the extent of 95%. What would be its osmotic pressure at 27°C? (R = 0.0821 L atm K-¹ mol-¹)

10.  When 2.56g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (Sx). (Kf for CS2 = 3.83 K kg mol-¹,atomic mass of sulphur = 32 gmol-1)


11. Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol-¹) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization. (Kf for water = 1.86 K kg mol-¹)

12. A 0.01 m aqueous solution of AlCl3 freezes at -0.068 °C. Calculate the percentage of dissociation. [Given: Kf for water = 1.86 K kg mol-¹]

13. Write four difference between ideal and non ideal solutions. 

14. Calculate the boiling point of the solution containing 1.8g of a non volatile solute dissolved in 90 g of benzene. The boiling  point of pure benzene is 353.23K. kb = 2.53 K kg mol‐¹, molar mass of solute 58 g mol-¹.  

15. When 1.80 gm of non volatile compound is dissolved in 25 g of acetone , the solution boils at 56.86 C  while pure acetone boils at 56.38⁰ C under the same atmospheric pressure calculate the molar mass of the compound. Kb for the acetone is 1.72 k kg mol-¹.

16. Specific conductance of 0.12 N solution of an electrolyte is 2.4 x 10-² S cm‐¹.Calculate equivalent conductance.

17. Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K2SO4 in 2 litres of water at 25°C assuming it to be completely dissociated.(Atomic masses: K = 39 u, S = 32 u, O = 16 u)

18. Determine the osmotic pressure of a solution prepared by dissolving           2.32 x 10-²g of K2SO4 in 2 L of solution at 25⁰ C assuming that K2SO4 is completely dissociated.

19. Calculate the freezing point of a solution containing 60 g of glucose (molar mass=180 g mol-¹) in 250g of water.(Kf of water = 1.86 K kg mol-¹)

20. Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2) is dissolved in 500 g of water. (Kf for water = 1.86 K kg mol-¹)

21. Some ethylene glycol, HOCH2CH2OH, is added to your car's cooling system along with 5 kg of water. If the freezing point of water-glycol solution is - 15.0°C, what is the boiling point of the solution?

(Kb= 0.52 K kg mol-¹ and Kf = 1.86 K kg mol-¹ for water)

22. 1.00 g of a non-electrolyte solute dissolved in 50 g of benzene lowered the freezing point of benzene by 0.40 K. The freezing point depression constant of benzene is 5.12 K kg mol-¹. Find the molar mass of the solute.

23. A 4% solution (w/w) of sucrose (M = 342gmol-¹) in water has a freezing point of 271.15 K. Calculate the freezing point of 5% glucose

(M = 180gmol-¹) in water. (Given: Freezing point of pure water = 273.15K )

24. An antifreeze solution is prepared by dissolving 31 g of ethylene glycol (Molar mass = 62 g mol-¹) in 600 g of water. Calculate the freezing point of the solution. (Kf for water = 1.86 K kg mol-¹)

25. Calculate the mass of compound (molar mass = 256 gmol-¹) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K.   (Kf = 5.12Kkgmol-¹).

26. Why is boiling point of 1M NaCl solution more than that of 1M glucose

 solution?

27. Out of the following 1.0 M aqueous solutions which one will show largest freezing point depression?

(a) NaCl
(b) Na2SO4
(C) C6H12O6
(d) Al2(SO4)3

28. Out of 0.1 molal aqueous solution of glucose and 0.1 molal aqueous solution of KCl, which one will have higher boiling point and why?

29. Give reasons:

(i) 0.1 M KCI has higher boiling point than 0.1 M glucose.

30. Give reason for the following:

Elevation of boiling point of 1m KCI solution is nearly double than that of 1m sugar solution.