Ch.13 - Solutions & Their Properties
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Problem 1
Ethanol 1CH CH OH 2 dissolves in hexane 1C H 2. Give the strongest type of intermolecular force between two sol- ute molecules, between two solvent molecules, and between a solute and solvent molecule. (LO 13.1) (a)
- When lithium chloride dissolves in water, the temperature of the solution increases. Which diagram represents the enthalpy changes of the steps in the solution-making process? (LO 13.2)
Problem 2
- In which solvent does sodium acetate 1CH COONa2 have the highest solubility (a) Acetone CH3OCH3 (b) Methanol (CH3OH) (c) Ethanol (CH3CH2OH) (d) Pentane (CH3CH2CH2CH2CH3)
Problem 3
Problem 4
Rubbing alcohol is a 90% (by mass) solution of isopropyl alcohol, C3H8O, in water. How many moles of isopropyl alcohol are in 50.0 g of rubbing alcohol? (LO 13.4) (a) 45 mol
- Fluoride ion is added to drinking water at low concentra- tions to prevent tooth decay. What mass of sodium fluoride (NaF) should be added to 750 L of water to make a solution that is 1.5 ppm in fluoride ion? (LO 13.5) (a) 1.1 g (b) 2.5 g (c) 0.51 g (d) 3.1 g
Problem 5
- Concentrated hydrochloric acid solution contains 37.0% by mass HCl. If the density is 1.18 g/mL, what is the molar concentration? (LO 13.6, 13.7) (a) 10.1 M (b) 16.2 M (c) 8.60 M (d) 12.0 M
Problem 6
- A 10.0 M aqueous solution of NaOH has a density of 1.33 g/cm3 at 25 C. Calculate the mass percent of the NaOH in the solution (a) 53.2% (b) 30.1% (c) 40.0% (d) 13.3%
Problem 7
- The molarity of a solution of sodium acetate (CH3COONa) at 20 C is 7.5 M. Use the graph showing the solubility of sodium acetate as a function of temperature to describe the solution. The solution is . (LO 13.7, 13.8)
Problem 8
(a) Saturated (b) Unsaturated (c) Supersaturated (d) Colloidal
- A scuba diver is breathing compressed air that is 21% (by volume) oxygen at a depth of 66 ft. beneath the surface. The total pressure at this depth is 3.0 atm. The Henry's law constant (k) for O2 in water at a normal body temperature (37 °C ) is 1.93 * 10-3 mol>(L atm). What is the solubility of O2 in the blood of the diver at 66 ft. beneath the surface? (LO 13.9) (a) 1.22 * 10-3 M (b) 2.76 * 10-2 M (c) 1.22 * 10-1 M (d) 2.76 * 10-1 M
Problem 9
- Which of the following solutions has the lowest vapor pres- sure? (Assume complete dissociation for ionic compounds.) (LO 13.10) (a) An aqueous solution of 0.25 m Ca1NO322 (b) An aqueous solution of 0.30 m sodium chloride (NaCl) (c) A mixture of 50 mL of water and 50 mL of ethanol 1CH3CH2OH2 (d) A mixture of 25 mL of water and 50 mL of ethanol 1CH3CH2OH2
Problem 10
- Acetone, C3H6O, and ethyl acetate, C4H8O2, are organic liquids often used as solvents. At 30 °C, the vapor pressure of acetone is 285 mm Hg, and the vapor pressure of ethyl acetate is 118 mm Hg. What is the vapor pressure in mm Hg at 30 °C of a solution prepared by dissolving 25.0 g of acetone in 25.0 g of ethyl acetate?
Problem 11
- 12. A solution contains 4.08 g of chloroform 1CHCl32 and 9.29 g of acetone 1CH3COCH32. The vapor pressures at 35 °C of pure chloroform and pure acetone are 295 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressure above the solution. (LO 13.12) (a) 256 torr (b) 314 torr (c) 325 torr (d) 462 torr
Problem 12
- How many kilograms of ethylene glycol (automobile anti- freeze, C2H6O2) dissolved in 3.55 kg of water are needed to lower the freezing point of water in an automobile radiator to - 22.0 °C? The molal freezing point depression constant for water is Kf = 1.86 1°C kg2>mol. (LO 13.13) (a) 0.865 kg (b) 0.0420 kg (c) 9.01 kg (d) 2.61 kg
Problem 13
- An aqueous solution of a certain organic compound has a density of 1.063 g/mL, an osmotic pressure of 12.16 atm at 25.0 °C, and a freezing point of -1.03 °C. The compound is known not to dissociate in water. What is the molar mass of the compound?
Problem 14
- Hemoglobin is a large molecule that carries oxygen in the body. An aqueous solution that contains 2.61 g of hemoglo- bin in 100.0 mL has an osmotic pressure of 7.52 mmHg at 25 °C. What is the molar mass of the hemoglobin? Assume hemoglobin does not dissociate in water. (LO 13.15) (a) 1.96 * 103 g>mol (b) 84.8 g/mol (c) 6.45 * 104 g>mol (d) 3.65 * 103 g>mol
Problem 15
- The following phase diagram shows part of the vapor- pressure curves for a pure liquid (green curve) and a solution of the first liquid with a second volatile liquid (red curve).
Problem 29
(a) Is the boiling point of the second liquid higher or lower than that of the first liquid?
- The following phase diagram shows part of the liquid–vapor phase-transition boundaries for pure ether and a solution of a nonvolatile solute in ether.
Problem 30
(b) What is the approximate mo#lal concentration of the sol-ute? [Kb for ether is 2.021°C kg2>mol.]
- Two beakers, one with pure water (blue) and the other with a solution of NaCl in water (green), are placed in a closed container as represented by drawing (a). Which of the draw- ings (b)–(d) represents what the beakers will look like after a substantial amount of time has passed?
Problem 33
- The following phase diagram shows a very small part of the solid–liquid phase-transition boundaries for two solutions of equal concentration. Substance A has i = 1, and substance B has i = 3. (a) Which line, red or blue, represents a solution of A, and which represents a solution of B? (b) What is the approximate melting point of the pure liquid solvent? (c) What is the approximate molal concentration of each solution, assuming the solvent has Kf = 3.0 °C/m?
Problem 35
- If a single 5-g block of NaCl is placed in water, it dissolves slowly, but if 5 g of powdered NaCl is placed in water, it dis- solves rapidly. Explain.
Problem 36
- Why do ionic substances with higher lattice energies tend to be less soluble in water than substances with lower lattice energies?
Problem 37
- Which would you expect to have the larger (more negative) hydration energy: K+ or Ba2+?
Problem 38
- Which would you expect to have the larger hydration energy, SO42- or ClO4-? Explain.
Problem 39
- Classify the strongest type of intermolecular force in the follow- ing interactions: solvent–solvent, solvent–solute, and solute– solute when solid iodine 1I22 is placed in the water. Based on these interactions, predict whether I2 is soluble in water.
Problem 40
- Classify the strongest type of intermolecular force in the following interactions: solvent–solvent, solvent–solute, and solute–solute when solid glucose (C6H12O6) is placed in water. Based on these interactions, predict whether glucose is soluble in water.
Problem 41
- What is the sign of ΔHsoln, and how will the temperature change when a solute dissolves with the following enthalpy changes? ΔHsolute = +56 kJ/mol, ΔHsolvent = +34 kJ/mol, ΔHsolute-solvent = -125 kJ/mol.
Problem 43
- Br₂ is much more soluble in tetrachloromethane (CCl₄) than in water. Explain.
Problem 44
- The following pictures represent solutions of AgCl, which also may contain ions other than Ag+ and Cl- that are not shown. If solution 1 is a saturated solution of AgCl, classify solutions 2–4 as unsaturated, saturated, or supersaturated. (1) (2) (3) (4)
Problem 45
- Is the solubility of acetic acid, CH3COOH, greater in water or benzene, C6H6?
Problem 46
- Predict whether the solubility of butane, C4H10, is greater in water or benzene, C6H6.
Problem 47