Ch.13 - Solutions & Their Properties
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- What is the vapor pressure in mm Hg of a solution of 16.0 g of glucose (C6H12O6) in 80.0 g of methanol (CH3OH) at 27 °C? The vapor pressure of pure methanol at 27 °C is 140 mm Hg.
Problem 103
- What is the freezing point in °C of each of the solutions in Problem 13.102? For water, Kf = 1.86 °C·kg/mol.
Problem 105
- A 1.0 m solution of K2SO4 in water has a freezing point of -4.3 °C. What is the value of the van’t Hoff factor i for K2SO4?
Problem 106
- The van’t Hoff factor for KCl is i = 1.85. What is the boiling point of a 0.75 m solution of KCl in water? For water, Kb = 0.511°C kg/mol.
Problem 107
- Cyclopentane 1C5H102 and cyclohexane 1C6H122 are vola- tile, nonpolar hydrocarbons. At 30.0 °C, the vapor pres- sure of cyclopentane is 385 mm Hg, and the vapor pressure of cyclohexane is 122 mm Hg. What is Xpentane in a mixture of C5H10 and C6H12 that has a vapor pressure of 212 mm Hg at 30.0 °C?
Problem 109
- The industrial solvents chloroform (CHCl₃) and dichloromethane (CH₂Cl₂) are prepared commercially by the reaction of methane with chlorine, followed by fractional distillation of the product mixture. At 25 °C, the vapor pressure of CHCl₃ is 205 mm Hg, and the vapor pressure of CH₂Cl₂ is 415 mm Hg. What is the vapor pressure in mm Hg at 25 °C of a mixture of 15.0 g of CHCl₃ and 37.5 g of CH₂Cl₂?
Problem 111
- What is the mole fraction of each component in the liquid mixture in Problem 13.110, and what is the mole fraction of each component in the vapor at 30 °C?
Problem 112
- What is the mole fraction of each component in the liquid mixture in Problem 13.111, and what is the mole fraction of each component in the vapor at 25 °C?
Problem 113
- A solution prepared by dissolving 5.00 g of aspirin, C9H8O4, in 215 g of chloroform has a normal boiling point that is elevated by ΔT = 0.47 °C over that of pure chloro- form. What is the value of the molal boiling-point-elevation constant for chloroform?
Problem 114
- A solution prepared by dissolving 3.00 g of ascorbic acid (vitamin C, C6H8O6) in 50.0 g of acetic acid has a freez- ing point that is depressed by ΔT = 1.33 °C below that ofpure acetic acid. What is the value of the molal freezing- point-depression constant for acetic acid?
Problem 115
- A solution of citric acid, C6H8O7, in 50.0 g of acetic acid has a boiling point elevation of ΔT = 1.76 °C. What is the molality of the solution if the molal boilin# g-point-elevation constant for acetic acid is Kb = 3.07 1°C kg2>mol.
Problem 116
- What is the osmotic pressure in atmospheres you would expect for each of the following solutions? (a) 5.00 g of NaCl in 350.0 mL of aqueous solution at 50 °C (b) 6.33 g of sodium acetate, CH3CO2Na, in 55.0 mL of aqueous solution at 10 °C
Problem 118
- Human blood gives rise to an osmotic pressure of approxi-mately 7.7 atm at body temperature, 37.0 °C. What must the molarity of an intravenous glucose solution be to give rise to the same osmotic pressure as blood?
Problem 121
- 13.122 When salt is spread on snow-covered roads at - 2 °C, the snow melts. When salt is spread on snow-covered roads at - 30 °C, nothing happens. Explain.
Problem 122
- If cost per gram were not a concern, which of the following substances would be the most efficient per unit mass for melting snow from sidewalks and roads: glucose 1C6H12O62, LiCl, NaCl, or CaCl2? Explain.
Problem 123
- Cellobiose is a sugar obtained by degradation of cellulose. If 200.0 mL of an aqueous solution containing 1.500 g of cellobiose at 25.0 °C gives rise to an osmotic pressure of 407.2 mm Hg, what is the molecular weight of cellobiose?
Problem 124
- The freezing point of a solution prepared by dissolving 1.00 mol of hydrogen fluoride, HF, in 500 g of water is -3.8 °C, but the freezing point of a solution prepared by dissolving 1.00 mol of hydrogen chloride, HCl, in 500 g of water is -7.4 °C. Explain.
Problem 126
- What is the reason behind the boiling point of a solution being 100.8 °C when 71 g of Na2SO4 is dissolved in 1.00 kg of water?
Problem 127
- When a 2.850 g mixture of the sugars sucrose (C12H22O11) and fructose (C6H12O6) was dissolved in water to a volume of 1.50 L, the resultant solution gave an osmotic pressure of 0.1843 atm at 298.0 K. What is Xsucrose of the mixture?
Problem 128
- Bromine is sometimes used as a solution in tetrachloro- methane, CCl4. What is the vapor pressure in mm Hg of a solution of 1.50 g of Br2 in 145.0 g of CCl4 at 300 K? The vapor pressure of pure bromine at 300 K is 30.5 kPa, and the vapor pressure of CCl4 is 16.5 kPa.
Problem 131
- There's actually much more in seawater than just dissolved NaCl. Major ions present include 19,000 ppm Cl-, 10,500 ppm Na+, 2650 ppm SO 2-, 1350 ppm Mg2+, 400 ppm Ca2+, 380 ppm K+, 140 ppm HCO3-, and 65 ppm Br-. (a) What is the total molality of all ions present in seawater?
Problem 133
- What is the van’t Hoff factor for K2SO4 in an aqueous solution that is 5.00% K2SO4 by mass and freezes at -1.21 °C?
Problem 135
- If the van’t Hoff factor for LiCl in a 0.62 m solution is 1.96, what is the vapor pressure depression in mm Hg of the solution at 298 K? (The vapor pressure of water at 298 K is 23.76 mm Hg.)
Problem 136
- What is the value of the van’t Hoff factor for KCl if a 1.00 m aqueous solution shows a vapor pressure depression of 0.734 mm Hg at 298 K? (The vapor pressure of water at 298 K is 23.76 mm Hg.)
Problem 137
- A solid mixture of KCl, KNO3, and Ba1NO322 is 20.92 mass % chlorine, and a 1.000 g sample of the mix- ture in 500.0 mL of aqueous solution at 25 °C has an osmotic pressure of 744.7 mm Hg. What are the mass percents of KCl, KNO3, and Ba1NO322 in the mixture?
Problem 138
- A solution of LiCl in a mixture of water and methanol 1CH3OH2 has a vapor pressure of 39.4 mm Hg at 17 °C and 68.2 mm Hg at 27 °C. The vapor pressure of pure water is 14.5 mm Hg at 17 °C and 26.8 mm Hg at 27 °C, and the vapor pressure of pure methanol is 82.5 mm Hg at 17 °C and 140.3 mm Hg at 27 °C. What is the composition of the solution in mass percent?
Problem 139
- At 60 °C, compound X has a vapor pressure of 96 mm Hg, benzene 1C6H62 has a vapor pressure of 395 mm Hg, and a 50:50 mixture by mass of benzene and X has a vapor pres- sure of 299 mm Hg. What is the molar mass of X?
Problem 141
- Desert countries like Saudi Arabia have built reverse osmo-sis plants to produce freshwater from seawater. Assume that seawater has the composition 0.470 M NaCl and 0.068 M MgCl2 and that both compounds are completely dissociated. (b) If the reverse osmosis equipment can exert a maximum pressure of 100.0 atm at 25.0 °C, what is the maximum volume of freshwater that can be obtained from 1.00 L of seawater?
Problem 142
- Elemental analysis of b@carotene, a dietary source of vitamin A, shows that it contains 10.51% H and 89.49% C. Dissolving 0.0250 g of b@carotene in 1.50 g of camphor gives a freezing- point depression of 1.17 °C. What are the molecular weight and formula of b@carotene? [Kf for camphor is 37.7 1°C kg2>mol.]
Problem 144
- The steroid hormone estradiol contains only C, H, and O; combustion analysis of a 3.47 mg sample yields 10.10 mg CO2 and 2.76 mg H2O. When dissolving 7.55 mg of estradiol in 0.500 g of camphor, the melting point of camphor is depressed by 2.10 °C. What is the molecular weight of estradiol, and what is a probable formula? [For camphor, Kf = 37.7 °C kg/mol.]
Problem 146