Chapter 2 Solutions

Question 1. Which of the following units is useful in relating concentration of solution with its vapour pressure?

(i) mole fraction

(ii) parts per million

(iii) mass percentage

(iv) molality

Question 2. On dissolving sugar in water at room temperature solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid?

(i) Sugar crystals in cold water.

(ii) Sugar crystals in hot water.

(iii) Powdered sugar in cold water.

(iv) Powdered sugar in hot water.

Question 3. At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is __________.

(i) less than the rate of crystallisation

(ii) greater than the rate of crystallisation

(iii) equal to the rate of crystallisation

(iv) zero

Question 4. A beaker contains a solution of substance ‘A’. Precipitation of substance ‘A’ takes place when small amount of ‘A’ is added to the solution. The solution is _________.

(i) saturated

(ii) supersaturated

(iii) unsaturated

(iv) concentrated

Question 5. Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon ____________.

(i) Temperature

(ii) Nature of solute

(iii) Pressure

(iv) Nature of solvent

Question 6. Low concentration of oxygen in the blood and tissues of people living at high altitude is due to ____________.

(i) low temperature

(ii) low atmospheric pressure

(iii) high atmospheric pressure

(iv) both low temperature and high atmospheric pressure

Question 7. Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s law?

(i) Methanol and acetone.

(ii) Chloroform and acetone.

(iii) Nitric acid and water.

(iv) Phenol and aniline.

Question 8. Colligative properties depend on ____________.

(i) the nature of the solute particles dissolved in solution.

(ii) the number of solute particles in solution.

(iii) the physical properties of the solute particles dissolved in solution.

(iv) the nature of solvent particles.

Question 9. Which of the following aqueous solutions should have the highest boiling point?

(i) 1.0 M NaOH

(ii) 1.0 M $Na_2SO_4$

(iii) 1.0 M $NH_4NO_3$

(iv) 1.0 M $KNO_3$

Question 10. The unit of ebulioscopic constant is _______________.

(i) K kg $mol^{–1}$ or K $(molality)^{–1}$

(ii) mol kg $K^{–1}$ or $K^{–1}$(molality)

(iii) kg $mol^{–1} K^{–1}$ or $K^{–1}(molality)^{–1}$

(iv) K mol $kg^{–1}$ or K (molality)

Question 11. In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M $MgCl_2$ solution is _____________.

(i) the same

(ii) about twice

(iii) about three times

(iv) about six times

Question 12. An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because _____________.

(i) it gains water due to osmosis.

(ii) it loses water due to reverse osmosis.

(iii) it gains water due to reverse osmosis.

(iv) it loses water due to osmosis.

Question 13. At a given temperature, osmotic pressure of a concentrated solution of a substance _____________.

(i) is higher than that at a dilute solution.

(ii) is lower than that of a dilute solution.

(iii) is same as that of a dilute solution.

(iv) cannot be compared with osmotic pressure of dilute solution.

Question 14. Which of the following statements is false?

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

(ii) The osmotic pressure of a solution is given by the equation $\Pi = CRT$ ( where C is the molarity of the solution).

(iii) Decreasing order of osmotic pressure for 0.01 M aqueous solutions of barium chloride, potassium chloride, acetic acid and sucrose is $BaCl_2 > KCl > CH_3COOH >$ sucrose.

(iv) 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.

Question 15. The values of Van’t Hoff factors for KCl, NaCl and $K_2SO_4$, respectively, are _____________.

(i) 2, 2 and 2

(ii) 2, 2 and 3

(iii) 1, 1 and 2

(iv) 1, 1 and 1

Question 16. Which of the following statements is false?

(i) Units of atmospheric pressure and osmotic pressure are the same.

(ii) In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.

(iii) The value of molal depression constant depends on nature of solvent.

(iv) Relative lowering of vapour pressure, is a dimensionless quantity.

Question 17. Value of Henry’s constant $K_H$ ____________.

(i) increases with increase in temperature.

(ii) decreases with increase in temperature.

(iii) remains constant.

(iv) first increases then decreases.

Question 18. The value of Henry’s constant $K_H$ is _____________.

(i) greater for gases with higher solubility.

(ii) greater for gases with lower solubility.

(iii) constant for all gases.

(iv) not related to the solubility of gases.

Question 19. Consider the Fig. 2.1 and mark the correct option.

(i) water will move from side (A) to side (B) if a pressure lower than osmotic pressure is applied on piston (B).

(ii) water will move from side (B) to side (A) if a pressure greater than osmotic pressure is applied on piston (B).

(iii) water will move from side (B) to side (A) if a pressure equal to osmotic pressure is applied on piston (B).

(iv) water will move from side (A) to side (B) if pressure equal to osmotic pressure is applied on piston (A).

Question 20. We have three aqueous solutions of NaCl labelled as ‘A’, ‘B’ and ‘C’ with concentrations 0.1M, 0.01M and 0.001M, respectively. The value of van’t Hoff factor for these solutions will be in the order______.

(i) $i_A < i_B < i_C$

(ii) $i_A > i_B > i_C$

(iii) $i_A = i_B = i_C$

(iv) $i_A < i_B > i_C$

Question 21. On the basis of information given below mark the correct option.

Information:

(A) In bromoethane and chloroethane mixture intermolecular interactions of A–A and B–B type are nearly same as A–B type interactions.

(B) In ethanol and acetone mixture A–A or B–B type intermolecular interactions are stronger than A–B type interactions.

(C) In chloroform and acetone mixture A–A or B–B type intermolecular interactions are weaker than A–B type interactions.

(i) Solution (B) and (C) will follow Raoult’s law.

(ii) Solution (A) will follow Raoult’s law.

(iii) Solution (B) will show negative deviation from Raoult’s law.

(iv) Solution (C) will show positive deviation from Raoult’s law.

Question 22. Two beakers of capacity 500 mL were taken. One of these beakers, labelled as “A”, was filled with 400 mL water whereas the beaker labelled “B” was filled with 400 mL of 2 M solution of NaCl. At the same temperature both the beakers were placed in closed containers of same material and same capacity as shown in Fig. 2.2.

At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.

(i) vapour pressure in container (A) is more than that in container (B).

(ii) vapour pressure in container (A) is less than that in container (B).

(iii) vapour pressure is equal in both the containers.

(iv) vapour pressure in container (B) is twice the vapour pressure in container (A).

Question 23. If two liquids A and B form minimum boiling azeotrope at some specific composition then _______________.

(i) A–B interactions are stronger than those between A–A or B–B.

(ii) vapour pressure of solution increases because more number of molecules of liquids A and B can escape from the solution.

(iii) vapour pressure of solution decreases because less number of molecules of only one of the liquids escape from the solution.

(iv) A–B interactions are weaker than those between A–A or B–B.

Question 24. 4L of 0.02 M aqueous solution of NaCl was diluted by adding one litre of water. The molality of the resultant solution is _____________.

(i) 0.004

(ii) 0.008

(iii) 0.012

(iv) 0.016

Question 25. On the basis of information given below mark the correct option.

Information : On adding acetone to methanol some of the hydrogen bonds between methanol molecules break.

(i) At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult’s law.

(ii) At specific composition methanol-acetone mixture forms maximum boiling azeotrope and will show positive deviation from Raoult’s law.

(iii) At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show negative deviation from Raoult’s law.

(iv) At specific composition methanol-acetone mixture will form maximum boiling azeotrope and will show negative deviation from Raoult’s law.

Question 26. $K_H$ value for Ar(g), $CO_2(g)$, HCHO (g) and $CH_4(g)$ are 40.39, 1.67, $1.83 \times 10^{–5}$ and 0.413 respectively.

Arrange these gases in the order of their increasing solubility.

(i) HCHO < $CH_4$ < $CO_2$ < Ar

(ii) HCHO < $CO_2$ < $CH_4$ < Ar

(iii) Ar < $CO_2$ < $CH_4$ < HCHO

(iv) Ar < $CH_4$ < $CO_2$ < HCHO

Question 27. Which of the following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent?

(a) nature of solute (b) temperature (c) pressure

(i) (a) and (c) at constant T

(ii) (a) and (b) at constant P

(iii) (b) and (c) only

(iv) (c) only

Question 28. Intermolecular forces between two benzene molecules are nearly of same strength as those between two toluene molecules. For a mixture of benzene and toluene, which of the following are not true?

(i) $\Delta_{mix}H$ = zero

(ii) $\Delta_{mix}V$ = zero

(iii) These will form minimum boiling azeotrope.

(iv) These will not form ideal solution.

Question 29. Relative lowering of vapour pressure is a colligative property because _____________.

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

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

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

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

Question 30. Van’t Hoff factor i is given by the expression _____________.

(i) $i = \frac{\text{Normal molar mass}}{\text{Abnormal molar mass}}$

(ii) $i = \frac{\text{Abnormal molar mass}}{\text{Normal molar mass}}$

(iii) $i = \frac{\text{Observed colligative property}}{\text{Calculated colligative property}}$

(iv) $i = \frac{\text{Calculated colligative property}}{\text{Observed colligative property}}$

Question 31. Isotonic solutions must have the same _____________.

(i) solute

(ii) density

(iii) elevation in boiling point

(iv) depression in freezing point

Question 32. Which of the following binary mixtures will have same composition in liquid and vapour phase?

(i) Benzene - Toluene

(ii) Water-Nitric acid

(iii) Water-Ethanol

(iv) n-Hexane - n-Heptane

Question 33. In isotonic solutions ________________.

(i) solute and solvent both are same.

(ii) osmotic pressure is same.

(iii) solute and solvent may or may not be same.

(iv) solute is always same solvent may be different.

Question 34. For a binary ideal liquid solution, the variation in total vapour pressure versus composition of solution is given by which of the curves?

(i)

(ii)

(iii)

(iv)

Question 35. Colligative properties are observed when _____________.

(i) a non volatile solid is dissolved in a volatile liquid.

(ii) a non volatile liquid is dissolved in another volatile liquid.

(iii) a gas is dissolved in non volatile liquid.

(iv) a volatile liquid is dissolved in another volatile liquid.

Question 36. Components of a binary mixture of two liquids A and B were being separated by distillation. After some time separation of components stopped and composition of vapour phase became same as that of liquid phase. Both the components started coming in the distillate. Explain why this happened.

Question 37. Explain why on addition of 1 mol of NaCl to 1 litre of water, the boiling point of water increases, while addition of 1 mol of methyl alcohol to one litre of water decreases its boiling point.

Question 38. Explain the solubility rule “like dissolves like” in terms of intermolecular forces that exist in solutions.

Question 39. Concentration terms such as mass percentage, ppm, mole fraction and molality are independent of temperature, however molarity is a function of temperature. Explain.

Question 40. What is the significance of Henry’s Law constant $K_H$?

Question 41. Why are aquatic species more comfortable in cold water in comparison to warm water?

Question 42. (a) Explain the following phenomena with the help of Henry’s law.

(i) Painful condition known as bends.

(ii) Feeling of weakness and discomfort in breathing at high altitude.

(b) Why soda water bottle kept at room temperature fizzes on opening?

Question 43. Why is the vapour pressure of an aqueous solution of glucose lower than that of water?

Question 44. How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the phenomenon involved in the process.

Question 45. What is “semi permeable membrane”?

Question 46. Give an example of a material used for making semipermeable membrane for carrying out reverse osmosis.

Question 47. Match the items given in Column I and Column II.

Question 48. Match the items given in Column I with the type of solutions given in Column II.

Question 49. Match the laws given in Column I with expresions given in Column II.

Question 50. Match the terms given in Column I with expressions given in Column II.

Question 51. Assertion : Molarity of a solution in liquid state changes with temperature.

Reason : The volume of a solution changes with change in temperature.

Question 52. Assertion : When methyl alcohol is added to water, boiling point of water increases.

Reason : When a volatile solute is added to a volatile solvent elevation in boiling point is observed.

Question 53. Assertion : When NaCl is added to water a depression in freezing point is observed.

Reason : The lowering of vapour pressure of a solution causes depression in the freezing point.

Question 54. Assertion : When a solution is separated from the pure solvent by a semipermeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.

Reason : Diffusion of solvent occurs from a region of high concentration solution to a region of low concentration solution.

Question 55. Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

(i) w/w (mass percentage)

(ii) V/V (volume percentage)

(iii) w/V (mass by volume percentage)

(iv) ppm. (parts per million)

(v) x (mole fraction)

(vi) M (Molarity)

(vii) m (Molality)

Question 56. Using Raoult’s law explain how the total vapour pressure over the solution is related to mole fraction of components in the following solutions.

(i) $CHCl_3$ (l) and $CH_2Cl_2$(l)

(ii) NaCl(s) and $H_2O$ (l)

Question 57. Explain the terms ideal and non-ideal solutions in the light of forces of interactions operating between molecules in liquid solutions.

Question 58. Why is it not possible to obtain pure ethanol by fractional distillation? What general name is given to binary mixtures which show deviation from Raoult’s law and whose components cannot be separated by fractional distillation. How many types of such mixtures are there?

Question 59. When kept in water, raisin swells in size. Name and explain the phenomenon involved with the help of a diagram. Give three applications of the phenomenon.

Question 60. Discuss biological and industrial importance of osmosis.

Question 61. How can you remove the hard calcium carbonate layer of the egg without damaging its semiprermiable membrane? Can this egg be inserted into a bottle with a narrow neck without distorting its shape? Explain the process involved.

Question 62. Why is the mass determined by measuring a colligative property in case of some solutes abnormal ? Discuss it with the help of Van’t Hoff factor.