Chapter 13: Physical Properties of Solutions

Transcription

1 1. A saturated solution A) contains more solute than solvent. B) contains more solvent than solute. C) contains equal moles of solute and solvent. D) contains the maximum amount of solute that will dissolve in that solvent at that temperature. E) contains a solvent with only sigma bonds and no pi bonds (i.e. only single bonds, with no double or triple bonds). 3. Heat of solution A) is never positive ( H soln 0), because the solute-solvent attraction is never weaker than the combination of the solute-solute attraction and solvent-solvent attraction. B) is always positive ( H soln > 0), because the solute-solvent attraction is always weaker than the combination of the solute-solute attraction and solvent-solvent attraction. C) is always zero ( H soln = 0), because the solute-solvent attraction is defined as the average of the solute-solute attraction and solvent-solvent attraction. D) is always negative ( H soln < 0), because the solute-solvent attraction is always stronger than the combination of the solute-solute attraction and solvent-solvent attraction. E) may be positive, zero, or negative, depending on the relative strength of the solute-solvent, solute-solute, and solvent-solvent attractive forces. 5. In which of the following solvents would you expect KBr to be most soluble? A) C 6 H 14 (hexane) D) CCl 4 (carbon tetrachloride) B) CH 3 CH 2 OH (ethanol) E) C 6 H 12 (cyclohexane) C) C 6 H 6 (benzene) 7. Which of the following compounds should be soluble in CCl 4? A) NaCl B) H 2 O C) NaOH D) C 8 H 18 E) None of these 9. A % by mass solution of lactose (C 12 H 22 O 11, g/mol) in water has a density of g/ml at 20 C. What is the molarity of this solution? A) M B) M C) M D) M E) M Page 226

2 11. Which of the following gives the molarity of a 17.0 % by mass solution of sodium acetate, CH 3 COONa (molar mass = 82.0 g/mol) in water? The density of the solution is 1.09 g/ml. A) M B) M C) 2.07 M D) 2.26 M E) 2.72 M 13. What is the molarity of a solution that is 7.00 % by mass magnesium sulfate and has a density of g/ml? A) M B) M C) M D) M E) 1.32 M 15. Determine the mass percent HCl in a 1.2 M solution of hydrochloric acid with a density of g/ml? A) 3.0 % B) 4.3 % C) 8.6 % D) 13% E) 30. % 17. Calculate the percent by mass of potassium nitrate in a solution made from 45.0 g KNO 3 and 295 ml of water. The density of water is g/ml. A) 1.51 % B) 7.57 % C) 13.3 % D) 15.2 % E) None of these 19. In how many grams of water should g of potassium nitrate (KNO 3 ) be dissolved to prepare a m solution? A) g B) g C) 1,000. g D) 1,263 g E) 7,917 g 21. What is the molality of a solution that is 3.68 % by mass calcium chloride? A) m B) m C) m D) m E) m 23. Calculate the molality of a 20.0% by mass ammonium sulfate (NH 4 ) 2 SO 4 solution. The density of the solution is g/ml. A) m B) 1.51 m C) 1.70 m D) 1.89 m E) 2.10 m 25. The density of a 20.3 M CH 3 OH (methanol) solution is g/ml. What is the molality of this solution? H 2 O is the solvent. A) 17.4 m B) 20.8 m C) 23.7 m D) 70.0 m E) 97.6 m 27. Which of the following has the greater molal concentration (molality)? A) 1.0 m KNO 3 B) 1.0 M KNO 3 C) Both have same molality. Page 227

3 29. Oxygen gas makes up 21 % of the atmosphere by volume. What is the solubility of O 2 (g) in water at 25 C if the atmospheric pressure is 741 mmhg? The Henry's law constant for oxygen gas at 25 C is mol/l atm. A) M D) M B) M E) 0.96 M C) M 31. The solubility of oxygen in lakes high in the Rocky Mountains is affected by the altitude. If the solubility of O 2 from the air is M at sea level and 25 C, what is the solubility of O 2 at an elevation of 12,000 ft where the atmospheric pressure is atm? Assume the temperature is 25 C, and that the mole fraction of O 2 in air is at both 12,000 ft and at sea level. A) M D) M B) M E) None of the above. C) M 33. The solubility of CO 2 gas in water A) increases with increasing gas pressure. B) increases with decreasing gas pressure. C) decreases with increasing gas pressure. D) is not dependent on pressure. 35. According to Raoult's law, which statement is false? A) The vapor pressure of a solvent over a solution decreases as its mole fraction increases. B) The solubility of a gas increases as the temperature decreases. C) The vapor pressure of a solvent over a solution is less than that of pure solvent. D) The greater the pressure of a gas over a solution the greater its solubility. E) Ionic solutes dissociate in solution causing an enhancement of all colligative properties. 37. The vapor pressure of water at 20 C is 17.5 mmhg. What is the vapor pressure of water over a solution prepared from g of sucrose (C 12 H 22 O 11 ) and g water? A) 0.51 mmhg D) 18.0 mmhg B) 16.0 mmhg E) 19.4 mmhg C) 17.0 mmhg Page 228

4 39. A solution of carbon tetrachloride in benzene, C 6 H 6, at 20 C has a total vapor pressure of mmhg. (Assume that this solution is ideal.) The vapor pressure of pure benzene at this temperature is mmhg and its density is g/cm 3 ; the vapor pressure of pure carbon tetrachloride is mmhg and its density is g/cm 3. What percentage of the volume of this solution is due to carbon tetrachloride? (Hint: assume that you have L of solution.) A) 75.2% B) 76.7% C) 14.3% D) 24.8% E) 23.3% 41. Dissolving a solute such as KOH in a solvent such as water results in A) an increase in the melting point of the liquid. B) a decrease in the boiling point of the liquid. C) a decrease in the vapor pressure of the liquid. D) no change in the boiling point of the liquid. 43. Which of the following aqueous solutions has the highest boiling point? K b for water is 0.52 C/m. A) 0.2 m KCl D) A and B. B) 0.2 m Na 2 SO 4 E) B and C. C) 0.2 m Ca(NO 3 ) During osmosis A) pure solvent diffuses through a membrane but solutes do not. B) pure solutes diffuse through a membrane but solvent does not. C) pure solvent and a solution both diffuse at the same time through a membrane. D) gases diffuse through a membrane into a solution and build up pressure. 47. What is the freezing point of a solution prepared from 50.0 g ethylene glycol (C 2 H 6 O 2 ) and 85.0 g H 2 O? K f of water is 1.86 C/m. A) 17.6 C B) 176 C C) 1.50 C D) 1.50 C E) 17.6 C 49. What is the molar mass of toluene if 0.85 g of toluene depresses the freezing point of 100. g of benzene by 0.47 C? K f of benzene is 5.12 C/m. A) 92.6 g/mol B) 78.0 g/mol C) 10.7 g/mol D) 81.8 g/mol E) 927 g/mol 51. When 24.0 g of glucose (a nonelectrolyte) are dissolved in 500. g of water, the solution has a freezing point of 0.47 C. What is the molar mass of glucose? K f of water is 1.86 C/m. A) 41.9 g B) 47.5 g C) 54.9 g D) 178 g E) 190. g Page 229

5 53. What is the freezing point of an aqueous solution of a nonvolatile solute that has a boiling point of C? For water K f = 1.86 C/m and K b = 0.52 C/m. A) 8.94 C B) 366 C C) 0.99 C D) 0.99 C E) 8.94 C 55. What volume of water should be added to 600. ml of ethanol in order to have a solution that boils at 95.0 C? (For ethanol, K b = 1.22 C/m, density = g/cm 3, boiling point = 78.4 C) A) 186 ml B) 245 ml C) 518 ml D) 116 ml E) 322 ml 57. When 12.1 g of the sugar sucrose (a nonelectrolyte) are dissolved in exactly 800 g of water, the solution has a freezing point of C. What is the molar mass of sucrose? K f of water is 1.86 C/m. A) 426 g B) 99.2 g C) 178 g D) 266 g E) 343 g 59. How many grams of sucrose (C 12 H 22 O 11, g/mol) would be needed to make 2.5 L of a solution with an osmotic pressure of 14 atm at 25 C? (R = L atm/k mol) A) 0.57 g B) 6.8 g C) g D) g E) g g of an unknown compound dissolved in 100. ml of water has an osmotic pressure of 28.1 mmhg at 20 C. Calculate the molar mass of the compound. A) 663 g/mol D) 727 g/mol B) g/mol E) g/mol C) 1.15 g/mol 63. An aqueous fructose solution having a density of g/cm 3 is found to have an osmotic pressure of 17.0 atm at 25 C. Find the temperature at which this solution freezes. [Given: for water K f = 1.86 C/m; molecular mass of fructose = g/mol] A) 1.52 C B) 1.30 C C) 1.57 C D) 1.69 C E) 1.41 C 65. What is the approximate Na + ion concentration in a 0.75 M Na 2 CO 3 solution? A) M B) 0.75 M C) 1.25 M D) 1.50 M E) 2.25 M 67. What is the osmotic pressure of a solution prepared from 13.7 g of the electrolyte HCl and enough water to make L of solution at 18 C? A) 0.55 atm B) 1.10 atm C) 8.95 atm D) 17.9 atm E) 35.9 atm Page 230

6 69. Arrange the following aqueous solutions in order of increasing boiling points: m Mg(NO 3 ) 2 ; m ethanol; m NaCl. A) Mg(NO 3 ) 2 < NaCl < ethanol D) NaCl < ethanol < Mg(NO 3 ) 2 B) ethanol < Mg(NO 3 ) 2 < NaCl E) Mg(NO 3 ) 2 < ethanol < NaCl C) ethanol < NaCl < Mg(NO 3 ) 2 Page 231