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Chapter 14
Solutions and Their Physical Properties
 
 
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 The effect of temperature on the vapor pressure of a liquid is illustrated.
Notes
 Vapor pressure vs temperature. A liquid in a closed container exerts a vapor pressure due to molecules that have escaped into the liquid phase. At equilibrium equal numbers of molecules leave and reenter the liquid phase. As the temperature is increased the average kinetic energy of the molecules increases. The higher kinetic energy of the liquid allows more molecules to escape, resulting in an increase in vapor pressure with increasing temperature.
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 Dissolution of NaCl in aqueous solution
Notes
 Dissolution of NaCl in water. When an ionic substance dissolves in water the ions are solvated by water molecules. The hydrogen atoms of the water molecule, which have a partial positive charge, interact with the chloride ion. The oxygen atom of the water molecule, which has a partial negative charge, interacts with the sodium ion. Each ion is surrounded by several water molecules.
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Notes
 Mixtures and compounds
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 Mixtures and compounds
Notes
 Mixtures and compounds
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 Removal of water from sugar by H2SO4
Notes
 Dehydration of sugar. The formula of table sugar is C12H22O11. Sugars were originally named carbohydrates (hydrates of carbon) because they have a ratio of H to O of 2:1. When H2SO4 is added to sugar, the sugar is converted to H2O and solid C. The reaction is exothermic so the water is converted to steam. A column of solid C rises out of the beaker during the reaction.
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 A solution of CuSO4 is prepared starting with solid CuSO4.
Notes
 Solution formation from a solid. A calculated amount of solid CuSO4 is weighed out and added to a volumetric flask. Some water is added and the flask is shaken to dissolve the solid. Once the CuSO4 has dissolved, enough water is added to make the volume exactly 250. mL. It should be pointed out that the volume of the solution may change as the CuSO4 dissolves so it must be completely dissolved before filling the volumetric flask to the mark.
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 Preparation of a dilute CuSO4 solution from a concentrated solution of CuSO4 is illustrated.
Notes
 Solution formation by dilution. A dilute solution of known concentration can be prepared from a more concentrated solution of known concentration. The volume of the concentrated solution required can be calculated using the equation Mi X Vi = Mf X Vf. The volume of the concentrated solution is measured with a pipet and transferred to a volumetric flask. Water is added, the solution is mixed, and more water is added to give the required volume.
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 Effect of pressure on the solubility of a gas
Notes
 Henry's law. The solubility of a gas in a liquid is proportional to the pressure of the gas over the liquid. Since volume and pressure are inversely proportional, decreasing the volume of the gas over the liquid increases its pressure. This causes more gas molecules to enter the liquid phase, resulting in an increased solubility. The relationship between the solubility of a gas and its partial pressure is given by Henry's law.
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 Effect of pressure on the solubility of a gas
Notes
 Henry's law. The solubility of a gas in a liquid is proportional to the pressure of the gas over the liquid. Since volume and pressure are inversely proportional, decreasing the volume of the gas over the liquid increases its pressure. This causes more gas molecules to enter the liquid phase, resulting in an increased solubility. The relationship between the solubility of a gas and its partial pressure is given by Henry's law.
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 Changes of state
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 Changes of state. As a solid is heated its temperature increases until its melting point is reached. At the melting point heat is used to convert the solid to a liquid at constant temperature. In the liquid state the temperatureincreases with added heat. At the boiling point the heat is used to convert the liquid to vapor at constant temperature. When the substance has vaporized, added heat causes the temperature of the vapor to increase.
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 Mobile ions are conductors of electricity
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 Electrolytes and non-electrolytes. In NaCl crystals the ions which are held in place by interactions between ions in the crystal lattice and cannot move in an electrical field. When NaCl is dissolved in water the water associates with the ions and separates them, allowing them to move freely in the solution. These mobile ions are good conductors of electricity. An aqueous solution of a nonelectrolyte such as sugar which contains no ions does not conduct electricity.
14.1
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 13-1
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 Preparation of an ethanol-water solution-Example 14-1 illustrated. A 10.00-mL sample of C2H5OH is added to some water in the volumetric flask. The solution is mixed and more water added to bring the total volume to 100.0 mL.
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14.2
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 13-2
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 Enthalpy diagram for solution formation. Depending on whether the broken arrow ends above, below, or on the line, the solution process is endothermic, exothermic, or has DHsoln 5 0, respectively.
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14.3
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 13-3
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 Representing intermolecular forces in a solution. The intermolecular forces of attraction represented here are between: (1) solvent molecules A (fn), (2) solute molecules B (fn), and (3) solvent A and solute B (fn).
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14.4
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 13-4
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 Two components of an ideal solution. Think of the OCH3 group in toluene (b) as a small “bump” on the planar benzene ring (a). Substances with similar molecular structures have similar intermolecular forces of attraction.
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14.5B
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 13-5
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 Intermolecular force between unlike molecules leading to a nonideal solution. Hydrogen bonding between CHCl3 (chloroform) and (CH3)2CO (acetone) molecules produces forces of attraction between unlike molecules that exceed those between like molecules.
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14.6
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 13-6
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 An ionic crystal dissolving in water. Clustering of water dipoles around the surface of the ionic crystal and the formation of hydrated ions in solution are the key factors in the dissolving process.
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14.7
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 13-7
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 Formation of a saturated solution. The lengths of the arrows represent the rate of dissolving (h) and the rate of crystallization (g). (a) When solute is first placed in the solvent only dissolving occurs. (b) After a time the rate of crystallization becomes significant. (c) The solution becomes saturated when the rates of dissolving and crystallization become equal.
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14.8
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 13-8
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 Water solubility of several salts as a function of temperature. Solubilities can be expressed in many ways: as molarities, as mass percent, or, as in this figure, grams of solute per 100 g H2O. For each solubility curve (as shown here for KClO4) points on the curve (S) represent saturated solutions. Regions above the curve (1) correspond to supersaturated solutions and below the curve (2), to unsaturated solutions.
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14.9
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 13-9
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 Recrystallization of KNO3. Crystals of KNO3 separated from an aqueous solution of KNO3 and CuSO4 (an impurity). The pale blue color of the solution is produced by Cu21, which remains in solution
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14.10
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 13-10
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 Effect of temperature on the solubilities of gases. Dissolved air is released as water is heated, even at temperatures well below the boiling point.
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14.11
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 13-11
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 Effect of pressure on the solubility of a gas. The concentration of dissolved gas (suggested by the depth of color) is proportional to the pressure of the gas above the solution (suggested by the density of the dots).
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14.12
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 Liquid-vapor equilibrium for benzene-toluene mixtures at 25 °C.
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14.3
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 13-13
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 Liquid-vapor equilibrium for benzene-toluent mixtures at 1 atm
14.14.1UN
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 P 553
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 oil refinery distillation (orig. 14.14.02.UN)
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 Fractional distillation
14.15
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 13-15
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Notes
 A minimum boiling point azeotrope
14.16
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 13-16
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 Observing the direction of flow of water vapor
14.17L
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 13-17
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 An illustration of osmosis
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14.18
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 Desalination of saltwater by reverse osmosis. The membrane is permeable to water but not to ions. The normal flow of water is from side A to side B. If we exert a pressure on side B that exceeds the osmotic pressure of the saltwater, a net flow of water occurs in the reverse direction-from the saltwater to the pure water. The lengths of the arrows suggest the magnitudes of the flow of water molecules in each direction
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14.19
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 13-19
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 Vapor pressure lowering by a nonvolatile solute. The normal freezing point and normal boiling point of the pure solvent are fp0 and bp0, respectively. The corresponding points for the solution are fp and bp. The freezing point depression, DTf, and the boiling point elevation, DTb, are indicated. Because the solute is assumed to be insoluble in the solid solvent, the sublimation curve of the solvent is unaffected by the presence of solute in the liquid solution phase. That is, the curve is the same for the two phase diagrams
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14.19.4UN
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 P 561
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 Dynamic equilibrium and solute disrupts equilibrium diagrams
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14.19.5UN
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 P 562
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 Svante Arrhenius (1859-1927)
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14.20a,b
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 13-20
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 Interionic attractions in aqueous solution. (a) A positive ion in aqueous solution is surrounded by a shell of negative ions. (b) A negative ion attracts positive ions to its immediate surroundings
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14.21
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 13-21
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 The Thndall effect
14.22
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 13-22
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 Surface of SiO2 particle in colloidal sil
14.23
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 13-23
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 Coagulation of colloidal iron oxide
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14.24
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 13-24
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Notes
 The principle of dialysis
14.24.1UN
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 P 566
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 Patient hooked up to a dialysis machine
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14-25
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 13-25
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 Graph showing a typical gas chromatogram with recorder reading vs time in minutes
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P 560
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P 628-3
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 Solution Formation from a solid
P 825-3a
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 Electrolytes and non-electrolytes
P 542
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Notes
 Inducing a dipole
P 560
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 Water sprayed on citurs fruit
P 560
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 Lowering the freezing point of water on roads
P 568
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 P 568
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 A chromatograph in use in a laboratory
Table 14.1
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 Table 14.1
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Notes
 Some common solutions
Table 14.2
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 Table 14.2
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Notes
 Freezing-point depression and boiling-point elevation constants
Table 14.3
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 Table 14.3
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Notes
 Variation of the van't Hoff Factor, I, with Solution molality