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- 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
- What osmotic pressure in mm Hg would you expect for an aqueous solution of 11.5 mg of insulin 1mol. weight = 59902 in 6.60 mL of solution at 298 K? What would the height of the water column be in meters? The density of mercury is 13.534 g/mL at 298 K.
Problem 119
- 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
- The van't Hoff factor for CaCl2 is 2.71. What is its mass % in an aqueous solution that has Tf = - 1.14 °C?
Problem 134
- 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
- A solution of 0.250 g of naphthalene (mothballs) in 35.00 g of camphor lowers the freezing point by 2.10 °C. What is the molar mass of naphthalene? The freezing-point-depression constant for camphor is 37.7 °C kg/mol.
Problem 143
- 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
- Addition of 50.00 mL of 2.238 m H2SO4 1solution density = 1.1243 g>mL2 to 50.00 mL of 2.238 M BaCl2 gives a white precipitate. (b) If you filter the mixture and add more H2SO4 solution to the filtrate, would you obtain more precipitate? Explain.
Problem 148
Problem 149a
Treatment of 1.385 g of an unknown metal M with an excess of aqueous HCl evolved a gas that was found to have a volume of 382.6 mL at 20.0 °C and 755 mm Hg pressure. Heating the reaction mixture to evaporate the water and remaining HCl then gave a white crystalline compound, MClx. After dissolving the compound in 25.0 g of water, the melting point of the resulting solution was - 3.53 °C. (b) What mass of MClx is formed? (a) How many moles of H2 gas are evolved?
Problem 149c
Treatment of 1.385 g of an unknown metal M with an excess of aqueous HCl evolved a gas that was found to have a volume of 382.6 mL at 20.0 °C and 755 mm Hg pressure. Heating the reaction mixture to evaporate the water and remaining HCl then gave a white crystalline compound, MClx. After dis- solving the compound in 25.0 g of water, the melting point of the resulting solution was - 3.53 °C. (c) What is the molality of particles (ions) in the solution of MClx?
Problem 149e
Treatment of 1.385 g of an unknown metal M with an excess of aqueous HCl evolved a gas that was found to have a volume of 382.6 mL at 20.0 °C and 755 mm Hg pressure. Heating the reaction mixture to evaporate the water and remaining HCl then gave a white crystalline compound, MClx. After dis- solving the compound in 25.0 g of water, the melting point of the resulting solution was - 3.53 °C. (e) What are the formula and molecular weight of MClx?
Problem 149f
Treatment of 1.385 g of an unknown metal M with an excess of aqueous HCl evolved a gas that was found to have a volume of 382.6 mL at 20.0 °C and 755 mm Hg pressure. Heating the reaction mixture to evaporate the water and remaining HCl then gave a white crystalline compound, MClx. After dis- solving the compound in 25.0 g of water, the melting point of the resulting solution was - 3.53 °C. (f) What is the identity of the metal M?
Problem 150a
A compound that contains only C and H was burned in excess O2 to give CO2 and H2O. When 0.270 g of the com- pound was burned, the amount of CO2 formed reacted completely with 20.0 mL of 2.00 M NaOH solution according to the equation 2 OH-1aq2 + CO21g2 S CO 2- 1aq2 + H2O1l2 When 0.270 g of the compound was dissolved in 50.0 g of camphor, the resulting solution had a freezing point of 177.9 °C. [#Pure camphor freezes at 179.8 °C and has Kf = 37.7 1°C kg2>mol.] (a) What is the empirical formula of the compound?
- Combustion analysis of a 36.72-mg sample of the male hormone testosterone gave 106.43 mg CO2 and 32.10 mg H2O as the only combustion products. When 5.00 mg of testosterone was dissolved in 15.0 mL of a suitable solvent at 25 °C, an osmotic pressure of 21.5 mm Hg was measured. What is the molecular formula of testosterone?
Problem 151
- A solution prepared by dissolving 100.0 g of a mixture of sugar 1C12H22O112 and table salt (NaCl) in 500.0 g of water has a freezing point of - 2.25 °C. What is the mass of each individual solute? Assume that NaCl is completely dissociated.
Problem 154