Chemistry Class 12 Chapter 2

1. The molality of pure water is

(a) 55.5

(b) 50.5

(c) 18

(d) 60.5

Ans (a)

2. The number of moles of NaCl in 3 litres of 3M solution is

(a) 1

(b) 3

(c) 9

(d) 27

Ans (c)

3. 4L of 0.02 M aqueous solution of NaCl was diluted by adding one litre of water. The molality of the resultant solution is ________

(a) 0.004

(b) 0.008

(c) 0.012

(d) 0.016

Ans (d)

4. Low concentration of oxygen in the blood and tissues of people living at high altitude is due to _________

(a) low temperature

(b) low atmospheric pressure

(c) high atmospheric pressure

(d) both low temperature and high atmospheric pressure

Ans (b)

5. Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s law?

(a) Methanol and acetone.

(b) Chloroform and acetone.

(c) Nitric acid and water.

(d) Phenol and aniline.

Ans (a)

6. Which of the following aqueous solutions should have the highest boiling point?

(a) 1.0 M NaOH

(b) 1.0 M Na₂SO₄

(c) 1.0 M NH₄NO₃

(d) 1.0 M KNO₃

Ans (b)

7. In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl₂ solution is _________

(a) the same

(b) about twice

(c) about three times

(d) about six times

Ans (c)

8. An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because _________ .

(a) it gains water due to osmosis.

(b) it loses water due to reverse osmosis.

(c) it gains water due to reverse osmosis.

(d) it loses water due to osmosis.

Ans (b)

9. Which of the following statements is false?

(а) Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.

(b) The osmotic pressure of a solution is given by the equation π = CRT (where C is the molarity of the solution).

(c) Decreasing order of osmotic pressure for 0.01 M aqueous solutions of barium chloride, potassium chloride, acetic acid and sucrose is
BaCl₂ > KCl > CH₃COOH > sucrose.

(d) According to Raoult’s law, the vapour pressure exerted by a volatile component of a solution is directly proportional to its mole fraction in the solution.

Ans (a)

10. The value of Henry’s constant KH is _________ .

(а) greater for gases with higher solubility.

(b) greater for gases with lower solubility.

(c) constant for all gases.

(d) not related to the solubility of gases.

Ans (b)

11. A solution containing 10 g per dm³of urea (molar mass 60 g mol^-1) is isotonic with 5% solution of non-volatile solute, MB of solute is

(a) 300 g mol^-1

(b) 350 g mol^-1

(c) 200 g mol^-1

(d) 250 g mol^-1

Ans (a)

12. What is mole fraction of solute in 1.00 m aqueous solution?

(a) 0.0354

(b) 0.0177

(c) 0.177

(d) 1.770

Ans (b)

13. When 1 mole of benzene is mixed with 1 mole of toluene (vapour pressure of benzene – 12.8 kPa, Toluene = 3.85 kPa)

(a) The vapour will contain equal amount of benzene and toluene.

(b) Not enough information is given for prediction.

(c) The vapour will contain a higher percentage of benzene.

(d) The vapour will contain higher percentage of toluene.

Ans (c)

14. At 100°C, the vapour pressure of a solution of 6.5 g of solute in 100 g of water is 732 mm. If Kb is 0.52 K/m, the boiling point of solution will be

(a) 102°C

(b) 103°C

(c) 101 °C

(d) 100°C

Ans (c)

15. If molality of dilute solution is doubled, the value of molal depression constant (Kf) will be

(a) halved

(b) tripled

(c) unchanged

(d) doubled

Ans (c)

16. The temperature at which 10% aqueous solution of (W/V) of glucose will show the osmotic pressure of 16.4 atom is (R = 0.082 L atom K^-1mol^-1)

(a) 360°C

(b) 180 K

(c) 300 K

(d) 360 K

Ans (d)

17. Which has the highest freezing point?

(a) 1 M glucose

(b) 1 M NaCl

(c) 1 M CaCl₂

(d) 1 M AlF₃

Ans (a)

18. Which of the following is correct.

(a) KJJ increases with increase in temperature (KH is Henry’s law constant).

(b) Solubility of gas in liquid decreases with increases in temperature.

(c) KJJ decreases with increase in temperature.

(d) Solubility of gas in liquid increases with increase in temperature.

Ans (a)

19. Benzoic acid, when dissolved in benzene, which of the following is correct.

(a) The benzoic acid will undergo dissociation.

(b) The benzoic acid will undergo association.

(c) Observed molar mass of benzoic acid in benzene will less than normal molar mass.

(d) Observed molar mass of benzoic acid in benzene is more than normal molar mass.

Ans (b)

20. Relative lowering of vapour pressure is a colligative property because ________ .

(а) It depends on the concentration of a non electrolyte solute in solution and does not depend on the nature of the solute molecules.

(b) It depends on number of particles of electrolyte solute in solution and does not depend on the nature of the solute particles.

(c) It depends on the concentration of a non electrolyte solute in solution as well as on the nature of the solute molecules.

(d) It depends on the concentration of an electrolyte or nonelectrolyte solute in solution as well as on the nature of solute molecules.

Ans (a)

21. Homogeneous mixture of two or more than two components is called

(a) solute

(b) solvent

(c) both (a) and (b)

(d) solution

Ans (d)

22. Which of the following is an example of gaseous solution ?

(a) Camphor is nitrogen gas

(b) Solution of hydrogen in palladium

(c) Chloroform mixed with nitrogen gas

(d) Both (a) and (c)

Ans (d) Both (a) and (c)

23. In amalgam of mercury with sodium, solvent is

(a) mercury

(b) sodium

(c) amalgam

(d) none of these

Ans (b)

24. What is the mole fraction of glucose in 10% w/W ‘ glucose solution ?

(a) 01

(b) 0.02

(c) 0.03

(d) 0.04

Ans (a)

25. A solution is obtained by mixing 200 g of 30 % and 300 g of 20% solution by weight. What is the percentage of solute in the final solution ?

(a) 50%

(b) 28%

(c) 64%

(d) 24%

Ans (d)

26. When 1.04 g of BaCl₂ is present in 105 g of solution the concentration of solution is

(a) 104 ppm

(b) 10.4 ppm

(c) 0.0104 ppm

(d) 104 ppm

Ans (b)

27. What will be the mole fraction of ethanol in a sample of spirit containing 85% ethanol by mass ?

(a) 0. 69

(b) 0.82

(c) 0.85

(d) 0.60

Ans (a)

28. What is the molarity of a solution containing 10 g of NaOH in 500 mL of solution ?

(a) 25 mol L^-1

(b) 0.75 mol L^-1

(c) 0.5 mol L^-1

(d) 1.25 mol L^-1

Ans (c)

29. What will be the molarity of 30 mL of 0.5 M H₂SO₄solution diluted to 500 mL ?

(a) 3 M

(b) 0.03 M

(c) 3 M

(d) 0.103 M

Ans (b)

30. How many Na⁺ions are present in 100 mL of 0.25 M of NaCl solution ?

(a) 025 x 10²³

(b) 1.505 x 10²²

(c) 15 x 10²²

(d) 2.5 x 10²³

Ans (b)

31. How many grams of NaOH are present in 250 mL of 0.5 M NaOH solution ?

(a) 32 g

(b) 3.8 g

(c) 5 g

(d) 0.5 g

Ans (c)

32. What will be the molality of a solution of glucose in water which is 10% w/W ?

(a) 01 m

(b) 0.617 m

(c) 0.668 m

(d) 1.623 m

Ans (b)

33. The molality of 648 g of pure water is …………….

(a) 36 m

(b) 5 m

(c) 3.6 m

(d) 5.55 m

Ans (d)

34. What is the mass of urea required for making 2.5 kg of 0.25 molal aqueous solution ?

(a) 37 g

(b) 25 g

(c) 125 g

(d) 27.5 g

Ans (a)

35. The law which indicates the relationship between solubility of a gas in liquid and pressure is_____________

(a) Raoult’s law

(b) Henry’s law

(c) Lowering of vapour pressure

(d) van’t Hoff law

Ans (b)