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# Che102 lecture3 pre_lecture

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### Che102 lecture3 pre_lecture

1. 1. 9/14/2011 Concentration of SolutionsQualitatively: dilute vs. concentrated.Qualitatively: dilute vs. concentrated.Quantitatively:1. Mass percent and parts per million: mass of component Mass % of component  x 100 total mass of solution mass of component parts per million  ppm  x 106 total mass of solutionQualitatively: dilute vs. concentrated.Quantitatively:1. Mass percent and parts per million: mass of component Mass % of component  x 100 total mass of solution mass of component parts per million  ppm  x 106 total mass of solutionExample: 1g glucose per 100 kg solution 1g [C6H12O6 ]  x 100  0.001 % 100,000 g 1g [C 6H12O 6 ]  x 10 6  10 ppm 100,000 g 1
2. 2. 9/14/2011Qualitatively: dilute vs. concentrated.Quantitatively:1. Mass percent and parts per million: mass of component Mass % of component  x 100 total mass of solution mass of component parts per million  ppm  x 10 6 total mass of solution mass of component parts per billion  ppb  x 10 9 total mass of solutionExample: EPA standard for arsenic (As) in drinking water = 0.010 ppm = 10 ppb Concentration of SolutionsQualitatively: dilute vs. concentrated.Quantitatively:2. Mole fraction: moles of component Mole fraction of component    total moles of all componentsExample: 1 mole glucose dissolved in 10 moles water 1 mol  C6H12O6   0.09 1 mol  10 mol Concentration of SolutionsQualitatively: dilute vs. concentrated.Quantitatively:3. Molarity: moles of solute Molarity  volume of solution (in liters)Example: 2.0 moles glucose dissolved in enough water to make 15 liters of solution 2.0 mol [C6H12O6 ]   0.13 M 15 L 2
3. 3. 9/14/2011 Concentration of SolutionsQualitatively: dilute vs. concentrated.Quantitatively:4. Molality: moles of solute Molality  mass of solvent (in kg)Example: 3.0 moles glucose dissolved in 12 kg of water 3.0 mol [C6H12O6 ]   0.25 m 12 kg Solubility Fig. 13.9Dynamic equilibrium: Dissolve solute + solvent solution CrystallizeSaturated solution: contains maximum amount of solutethat will dissolve in solution. Solubility: conc. of solute in a saturated solution. NaCl(s) Na+(aq) + Cl-(aq) Unsaturated solution: contains less than maximum amount of solute that will dissolve in the solvent. Types of Solutions • Supersaturated – In supersaturated solutions, the solvent holds more solute than is normally possible at that temperature. – These solutions are unstable; crystallization can usually be stimulated by adding a “seed crystal” or scratching the side of the flask. © 2009, Prentice-Hall, Inc. 3
4. 4. 9/14/2011 Factors Affecting Solubility1. Structural Factors: Like Dissolves Like Hexanol ButanolEthanol Factors Affecting Solubility1. Structural Factors: Like Dissolves Like hexane H H H H H H Are hexane and water miscible? H C C C C C C H H H H H H H water - - O - H H Factors Affecting Solubility1. Structural Factors: Like Dissolves Like immiscible hexane H H H H H H H C C C C C C H H H H H H H hexane water - water - O - H H 4
5. 5. 9/14/2011 Factors Affecting Solubility1. Structural Factors: Like Dissolves Like C N O F Ne Ar Kr Glucose (which has hydrogen bonding) is very soluble in water, while cyclohexane (which only has dispersion forces) is not. © 2009, Prentice-Hall, Inc. Factors Affecting Solubility1. Structural Factors: Like Dissolves Like Strong intermolecular interactions between High solubility solute and solvent 5
6. 6. 9/14/2011 Factors Affecting Solubility2. Pressure Effects:A) Does external pressure influence solubility of gas in liquid? Factors Affecting Solubility2. Pressure Effects:A) Does external pressure influence solubility of gas in liquid? Carbonated drinks: k(CO2) = 3 x 10-2 mol L-1 atm-1 P(CO2) during bottling = 3-5 atm S(CO2) = 0.1 – 0.2 M equal rates Dynamic equilibrium P(CO2) ambient = 3 x 10-4 atm S(CO2) ambient = 1 x 10-5 M Henry’s Law: Sg = kPg Sg = solubility of gas in solution k = Henry’s Law Constant Pg = partial pressure of gas above solution Fig. 13.14 Factors Affecting Solubility2. Pressure Effects:A) Does external pressure influence solubility of gas in liquid?B) Does external pressure influencesolubility of solid in liquid?C) Does external pressure influencesolubility of liquid in liquid? Fig. 13.14 6
7. 7. 9/14/2011 Factors Affecting Solubility3. Temperature Effects: Solubility of gases in water Hsoln < 0 Fig. 13.18 Factors Affecting Solubility3. Temperature Effects: Solubility of salts in water Hsoln varies Fig. 13.17Colligative properties: depend on the number of solute particles, not the nature of theparticles. Among colligative properties are Vapor pressure lowering Boiling point elevation Melting point depression Osmotic pressure 7
8. 8. 9/14/2011 Colligative Properties: Vapor PressureVapor pressure: pressure exerted by a liquid’s vapor when the liquid and vapor are indynamic equilbrium. Fig. 11.22 Colligative Properties: Vapor Pressure Which is greater? A B Vapor pressure A or Vapor pressure B? Raoult’s Law: Psoln = solventP°solvent Pure liquid Solution with Psoln = vapor pressure of solution nonvolatile solute solvent = mole fraction of solvent P°solvent = vapor pressure of pure solvent Colligative Properties: Vapor Pressure - + O +Solution with two volatile liquids H H - ORaoult’s Law: Acetone +CPtotal = PA + PB = AP°A + BP°B H 3C CH3 Hsolution < 0 Ideal solution Nonideal solution Ideal or non-ideal? 8
9. 9. 9/14/2011 Colligative Properties: Vapor Pressure Benzene Toluene HSolution with two volatile liquids H H C H H C H H C HRaoult’s Law: C C C C C C C CPtotal = PA + PB = AP°A + BP°B H C H H C H H H Hsolution ~ 0 Ideal solution Nonideal solution Ideal or non-ideal? 9