Colligative Properties - Liquid Solutions

GIIT CLASSES 15-B, YOGI VIHAR, HARIDWAR, UTTARAKHAND

COLLIGATIVE PROPERTIES

(OBJECTIVE SHEET)

1.A solution of x moles of sucrose in 100 grams of water freeze at –0.2°C. As ice separately the freezing point gas down to – 0.25°C. How many grams of ice would have separates? (a) 18 grams (b) 26 grams (c) 25 grams (d) 23 grams 2. In the preceding problem, what is the range of the change in molality (caused by formation of ice) to the original molality ? (a) 0.25 (b) 0.2 (c) 0.05 (d) 0.025 3. Three solutions (a) 12 N (b) 6 N and (c) 2N of HCl are available. If it is required to produce 4 N HCl be mixing them in the volume ratio x:y:z, which of the following ratios would be correct ? (a) 1:1:5 (b) 1:2:6 (c) 2:1:9 (d) 1:2:4 4. A solution contains x grams of glucose and y grains area in a kilogram of water. If the total weight of the solutes and the total solubility of the solution are w and m respectively, what is the magnitude of x/y in terms of w and m? [3(w-60m)/(180m-w)] (b) [3(w-180m)/(60m-w)] (c) 3(60m-w) (d) (180m-w) 5. A certain ideal mixture of liquids A and B has mole fractions of 0.25 and 0.50 for A in the vapour phase and the liquid phase respectively at a certain temperature. What would be the mole fraction of B in the vapour, when the mole fraction of A in the liquid is 0.25? (a) 0.95 (b) 0.9 (c) 0.75 (d) 0.85 6.In an ideal mixture of liquids A and B the mole fraction of A is 0.25. If the ratio of PA to PB is 7/3, how many repeated distillation would be required as a “minimum” to obtain a small quantity of distillate which has a mole fraction of A, better than 0.80? (a) 4 (b) 2 (c) 3 (d) 5 7.Equal volumes of two liquids, X and Y are mixed in form a homogenous solution. On mixing there is a volume contraction of7%. If the densities of the pure liquids X and Y are 0.80 gram per ml and 1.00 gm per ml respectively, calculate the molarities of X and Y in the solution. Molecular weights of X and Y are 46 and 18 respectively. (a) 8.73, 30.78

(b) 8.73, 29.87

(c) 9.45, 50.78

(d) 8.35, 20.87

8. The vapour pressure of a solution of 5x10-3 kg of non-electrolyte in 0.1 kg at water decreases from the value for pure solvent by 15 N/m². The molecular weight of the solution is (a) 180 (b) 90 (c) 270 (d) 200 9. The molality of 1 litre solution with X(%) H2SO4 is 9. The weight of solvent pressure of the solution is 910 grams. The percentage of the H2SO4 solution is (a) 90 (b) 80.26 (c) 40.13 (d)9 10. The molality of a solution of a substance X in water is 1.54. If 177 grams of X are dissolved in 2500 grams of water to obtain this molality, them the molecular weight of X is (a) 45.97 (b) 4.597 (c) 0.071 (d)459.7 11. The amount in kilograms of wet NaOH containing 12% water required to prepare 60 litre of 0.5 N solution is (a) 1.36 (b) 13.6 (c) 12 (d) 0.5 12. The mole fraction of C2H5OH in an aqueous solution that is simultaneously 3.86 m C2H5OH is (a) 0.214 (b) 0.386 (c) 0.555 (d) 0.063 . 13.The vapour pressure of a solution consisting of 43.68 g of C12H22O11 in 245 ec of water at 25°C is (density of water = 0.9971 g/ml, vapour pressure of pure water = 24.756 mm). (a) 2.353 (b) 23.53 (c) 235.3 (d) 0.2353 14. The decrease in freezing point of a aqueous solution of molarity 0.05 is (Density of solution = 0.95 g/cc, Kf =1.86; the solute is C6H12O6). (a) 0.099°C (b) 0.99°C (c) 0°C (d) 100.099°C 15. The relative lowering of vapour pressure of a solution is 0.005. If n2 moles of solute are dissolved in 180 grams of water, the value of n2 is (a) 0.005 (b) 0.0502 (c) 0.502 (d) 502 16. Elevation of boiling point studies of Ca(NO)2 give molar mass as 65.6. The degree of dissociation of Ca(NO3)2 is (a) 100% (b) 75% (c) 50% (d) 25% 17. The degree of association of phenol is 71.5% in benzene. The molar mass of phenol obtained from depression of freezing point studies is (a) 14.63 (b) 146.3 (c) 329.8 (d)32.98 18.Which of the following is a 1 molar solution? (a )6.4 grams of ethanol in 1000 ml of solution (b)11.098 grams of calcium chloride in 100 ml of solution (c) 0.22 grams of methanol in 10 ml of solution (d)5.85 grams of NaCl in 100 ml of solution 19. The purity of concentrated H2SO4 (Sp. gravity = 1.8), 5 ml which is neutralized by 5 ml of 3M NaOH is (a) 89.8 (b) 40.0 (c) 8.98 (d) 100 20. The molarity of a 45% solution of HCl which has a density 1.2 g/ml is (a) 1.2 (b) 4.5 (c) 14.79 (d)1.479 21. The van’t Hoff factor I, when α is the degree of dissociation electrolyte in solution and n is the number of ions formed is (a) α (n-1)-1 (b) α (1-n)-1 (c) α (1-n)+1 (d) α (n-1)+1 22. The vapour pressure of a dilute aqueous solution of glucose (C6H12O6) is x mm of Hg at 373 K. The mole fraction of the solvent is (a) x (b) 2x (c) 0.5 x (d) 1.5x 23.The molarity and molality of an aqueous solution of H2SO4 are M1 and M2 respectively. If the molecular mass of H2SO4 is M, the density of the solution is (A) M1 [(1/M2) + (M/1000)]g ml-1 (b) M2 [(1/M1) + (M/1000)]g ml-1 -1 (c) M1 [(M2) + (M/1000)]g ml (d) None 24.Two liquids A and B ate mixed at temperature T in a certain ratio to form an ideal solution. It is found that the partial vapour pressure of A i.e. pA is equal to pB. The vapour pressure of B for the liquid mixture. What is the total pressure of the liquid mixture in terms of p°A and p°B (the vapour pressures of the pure liquids A and B at the temperature)? (a) p°Ap°B/(p°A +p°B) (b) 2p°Ap°B/(p°A +p°B) (c) p°A /(p°A +p°B) (d) 2p°B /(p°A +p°B) 25. The vaporization of liquid water is endothermic to the extent of 9720 calories per mole. What be the entropy change given that the normal boiling point is 100°C? (a)9720/100 cal. deg-1 mol-1 (b) 9720/373cal. deg-1 mol-1 +(c) 9720/273cal. deg-1 mol-1 (d) (9720)(1/273 − 1/373) cal. deg-1 mol-1

26.Two liquids A and B form an ideal solution for which at a given temperature the vapour pressure P is given the equation P(mm) = 120x + 135, where x is the mole fraction of A. What is the ratio of the vapour pressure of the pure liquids A and B? (a) 8:9 (b) 9:8 (c) 17:9 (d) 18:17 27. In the problem( 26), what is the difference in vapour pressure of two solutions with mole fraction values x = x1 = 1/3 and x = x2 = 2/3? (a) 60 mm (b) 40 mm (c) 50 mm (d)100 mm 28. Two liquids A and B have vapour pressure in the ratio p°A: p°B = 1:2 at a certain temperature. Suppose we have an ideal solution A and B in the mole fraction ratio A:B = 1:2 what would be the mole fraction of A in the vapour in equilibrium with the solution at the given temperature ? (a) 0.25 (b) 0.2 (c) 0.5 (d) 0.33 29. A certain pure has a vapour pressure at 30°C. By dissolving x games of a nonclative solute in y grams of the pure liquid the vapour pressure is lowered by one-tweniteth if it forms value. If the molecular weight of the solute is 5 times the molecular weight of the liquid solvent what is the ratio x:y ? (a) 5:19 (b) 1:19 (c) 1:20 (d)5:20 30. The vapour pressure of water at 25°C is 28.3 torr. What is the vapour pressure of a solute containing 6 grams of urea in 180 grams of water at 28°C? (a) 27.8 torr (b) 25.6 torr (c) 27.1 torr (d) 28.07 torr 31. Which of the following solutions will have the highest freezing point? (i) 0.05 M NaCl (ii) 0.1 M BaCl2 (iii) 0.15 M urea. (a) (ii) (b) (iii) (c) (i) (d) both (ii) and (iii) 32.The Van’t Hoff’s factor for Ca(NO3)2 is 2.5. Using the dissociation equilibrium Ca(NO3)2 Ca2+ + 2NO3−the degree of dissociation obtained is (a) 0.25 (b) 0.75 (c) 0.33 (d) 0.66 33. Phenol associates to form dimer. The molar mass observed from freezing point depression measurement is 146.3. The degree of association is (a) 0.715% (b) 7.15 % (c) 71.5^% (d) 0.358% 34. The freezing point of H2O is lowered from 0°C to −17.8°C by adding CH3OH. The volume of CH3OH (density 0.787 g/ml) to be added to 10 litres of water is [Kf for H2O = 1.86] (a) 38.12 litres(b) 3.8912 litres(c) 3891.2litres (d) 3062.4 litres 35. When 1gm of Arsenic is added to 86 gm of Benzene the freezing point of Benzene is lowered by 0.19°C. (Kf = 4.9). The formula of Arsenic is (a) As2 (b) As3 (c) As4 (d) As 36. The mole fraction of a solute is 0.0033. The lowering of vapour pressure is 0.06 torr. The vapour pressure of solvent is (a) 180 torr (b) 1.8 torr (c) 18 torr (d) 0.18 torr 37. A solution of acid has molality 0.102 m. The degree of dissociation is 4.5%. The freezing point depression is (a) 0.199°C (b) 0.190°C (c) 0.009°C (d) 1.99°C 38. An aqueous solution containing 0.25 moles of X, a strong electrolyte in 500g of water freezes at −2.79°C, how many ions are formed per formula unit of X? [Kf = 1.86°C) (a) 1 (b) 2 (c) 3 (d) 4 39. An aqueous solution of urea contains 10% urea by weight. How much water is present in one kilogram of the solution? (a) 100 g (b) 200 g (c) 900 g (d)600g 40. How many litres of NH3 gas at STP will be needed to prepare 50 ml of 2.5 M ammonium hydroxide ? (a) 1.4l (b) 2.8 l (c) 0.56l (d)0.06l 41.A certain liquid has a vapour pressure of 440.0 mm at 20°C, which is lowered to 412.7 mm by dissolving 50 g of a nonvolatile solute in a kilogram of the liquid. If the molecular weight of the solute is 60, what is the molecular weight of the solvent? (a) 58 (b) 78.95 (c) 92 (d) 66 42. Using the data in the preceding problem, calculate the elevation of the boiling point ∆Tb for the solution given above. Kb for the liquid is 2.11 deg molal-1 (a) 0.758° (b) 1.578° (c) 1.758° (d) 0.912° 43. Calculate the ratio Kb/Kf for a liquid for which Tb/Tf = [Boiling point/Freezing point] = 1.366 and tb/tf = [Latent hat of vaporization/latent heat of fusion] = 6.75 (a) 0.276 (b) 0.333 (c) 0.191 (d) 0.227 44. The vapour pressure of water at 20°C is 17.33 mm. What is the density of water vapour is g/ml? (a) 1.217x10-5 (b) 2.171x10-5 (c) 2.711 x 10-5 (d) 1.712x10-5 45. Using the information in the preceding problem, calculate the vapour pressure of a solution of glucose in water (at 20°C) which has an osmotic pressure of 3atm. (a) 17.11 mm (b) 17.25 mm (c) 17.09 mm (d) 17.35 mm + 46.Calculate the concentration x and y respectively of potassium ion K and chloride ion Cl− in a solution obtained by mixing 20 ml of 0.1 M NaCl, 30 ml of 0.2M KCl, 25 ml of KNO3 (0.15 M) and finally making upto 100 ml. (a) 0.06 = x (b) 0.0975 = x (c) None 0.0375 = y 0.08 = y 47.An aqueous solution contains 10 grams of sucrose in 250 ml of the solution. Inversion in set in and 7 grams of sucrose have already reacted to form glucose and fructose at the time of measurement. What would be the freezing point of the solution? Assume that the density of the solution = 1.04 gram/ml, Kf for water = 1.86 deg/mola (a) –0.279 °C (b) –0.186°C (c) –0.37°C (d) –0.46 °C 48.The vapour pressure of ethyl acetate and methyl butyrate at 80°C are 833 mm and 361 mm respectively. What is the composition (mole ratio) of a mixture of the two liquids that boil at 80°C ? (a) 4.3:1 (b) 3.6:1 (c) 2.91:1 (d)5.45:1 49. In the preceding problem, what would be the mole fraction of ethyl acetate in the vapour equilibrium with the liquid mixture which boils at 80°C? Use the data from the preceding problem ? (a) 0.811 (b) 0.926 (c) 0.753 (d)0.672 50.An aqueous solution ‘A’ contains x grams of urea and y grams of glucose, both dissolved in 1000 grams of water. Solution ‘B’ has π/2 grams of glucose in 1000 grams of water. If both A and B freeze at the same temperature, what is the ratio of x and y? (a) 2:3 (b) 3:2 (c) 2:1 (d) 1:2